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F_DEXZ – Advanced Six Operator FM Synthesizer

F_DEXZ is a six-operator FM synthesizer designed for classic digital FM sounds, modern modular sound design, DX-style patch exploration, and hands-on experimental synthesis. It combines algorithm-based operator routing with editable envelopes, ratio and fixed-frequency operation, operator waveforms, feedback systems, stereo spread, internal LFO modulation, assignable modulation routing, polyphonic voice handling, UNI-style stacking, DX-style envelope editing, and DX7 SysEx patch import.

Important: Although F_DEXZ supports DX7 SysEx patch import and follows the classic six-operator FM concept, it is not intended to be a mathematically exact DX7 clone. Imported patches are translated into the DEXZ synthesis engine and may sound different from original Yamaha hardware or dedicated DX emulations.

Differences may occur because of operator scaling, waveform behaviour, feedback response, envelope timing, internal level handling, stereo processing, modulation behaviour, interpolation, and other engine-specific characteristics. Some imported patches may therefore require manual adjustment after import.

The goal of the DX7 import system is practical compatibility and creative reuse of classic FM patch libraries inside a modern modular environment, rather than bit-identical reproduction of the original hardware.

At its core, F_DEXZ follows the classic six-operator FM idea: operators can be arranged as carriers, modulators, or deeper modulation chains. A carrier is heard directly. A modulator changes the frequency or phase behaviour of another operator and therefore changes the tone. This means that in FM synthesis the most important sound-shaping controls are not only volume and pitch, but also operator level, frequency ratio, envelope shape, feedback, and routing.

F_DEXZ is not intended to be a simple preset player. It exposes the structure of FM synthesis so that the sound can be built, edited, animated, and pushed far beyond traditional electric pianos and bells. It can create classic FM keys, basses, metallic percussion, plucked tones, glassy pads, drones, harsh digital textures, stereo motion, evolving harmonic structures, and imported DX-style sounds.

Basic FM Concept

In frequency modulation synthesis, one oscillator can influence another oscillator. The oscillator that is heard directly is called a carrier. The oscillator that modifies another oscillator is called a modulator. When a modulator affects a carrier, new harmonics and sidebands are created. These sidebands give FM synthesis its bright, metallic, glassy, woody, electric, or percussive character.

The relationship between operator frequencies is extremely important. Simple ratios such as 1.00, 2.00, 3.00, or 0.50 usually create harmonic tones that feel stable and musical. More unusual ratios create inharmonic sidebands, which are useful for bells, gongs, struck metal, percussion, noise-like attacks, and experimental sounds.

FM synthesis is very sensitive. A small change in operator level, envelope timing, ratio, or feedback can completely change the sound. This is part of its strength, but it also means that good FM programming usually starts with simple structures and gradually adds complexity.

Operators

F_DEXZ contains six operators. Each operator is an oscillator with its own level, frequency settings, waveform, envelope, feedback behaviour, and on/off state. Depending on the selected algorithm, an operator may be heard directly as a carrier, may only modulate another operator, or may be part of a longer modulation chain.

An operator that is a carrier mainly contributes audible volume. An operator that is a modulator mainly contributes tone, brightness, attack character, metallic detail, or movement. This distinction is essential. Raising the level of a carrier makes the sound louder. Raising the level of a modulator can make the sound brighter, harsher, more complex, or more unstable.

Operators can be switched on or off. Turning off an operator removes it from the sound structure. This is useful for isolating parts of a patch, simplifying an algorithm, checking whether an operator is acting as a carrier or modulator, or building a patch one operator at a time.

User Wave Import (.DZW)

In addition to the built-in operator waveforms, F_DEXZ supports user-defined single-cycle waveforms created with the companion F_DRAWWAVE module.

F_DRAWWAVE can export waveforms as .DZW files. These files contain a high-resolution single-cycle wavetable which can be loaded directly into individual operators inside F_DEXZ.

Each operator includes a small Wave Load button in the operator header. Press this button to browse the DEXZ Waves folder and select a .DZW waveform.

The source selection popup highlights the currently active source. Selecting a different source immediately changes the waveform used by that operator without affecting envelopes, ratios, levels, modulation routing, or other operator settings.

After loading a waveform, the operator automatically switches to the USER waveform mode. The waveform selector now provides five waveform types:

• Sine
• Saw
• Square
• Triangle
• User Wave (.DZW)

Every operator can load a different waveform. For example, Operator 1 may use a vocal-style waveform, Operator 2 a metallic waveform, and Operator 3 a custom harmonic shape created in F_DRAWWAVE.

This allows FM structures that go far beyond traditional DX-style sine-wave FM. Complex harmonic content can be introduced directly at the operator level, creating spectra that would normally require many stages of modulation.

Loaded user waves are stored inside the preset and are automatically restored when the preset is loaded again. The original .DZW file is only required when importing the waveform for the first time.

User waves may be used as carriers, modulators, or both. Particularly interesting results can be achieved when custom harmonic waveforms are used as modulators inside multi-operator FM algorithms.

Because each operator can load its own waveform independently, F_DEXZ effectively combines wavetable-style oscillator design with classic six-operator FM synthesis.

Wave: Selects the oscillator waveform used by the operator. Available modes are Sine, Saw, Square, Triangle, and User Wave. User Wave becomes available after loading a .DZW waveform from F_DRAWWAVE.

Carriers and Modulators

A carrier is an operator that reaches the audio output. If only a carrier is active, it behaves much like a normal oscillator with an envelope. A modulator is an operator that does not necessarily reach the output directly, but instead changes another operator. A modulator can therefore have a large effect even when it is not directly audible by itself.

If a patch is silent, the selected algorithm may not have an active carrier, or the carrier level or envelope may be too low. A modulator alone may not produce sound if it is not routed to the output. When troubleshooting, always first identify which operators are carriers in the selected algorithm.

Unlike a traditional DX7, operators in F_DEXZ are not limited to sine waves. Any operator may use one of the built-in waveforms or an imported User Wave. This applies equally to carriers and modulators.

Using custom waveforms as modulators can create extremely rich spectra with fewer modulation stages than would normally be required in classic sine-wave FM synthesis.

Algorithms

The algorithm determines how the six operators are connected. Some algorithms use long modulation chains, where one operator modulates another, which modulates another, which finally modulates a carrier. These structures are useful for complex, evolving, metallic, or highly animated sounds.

Other algorithms use several parallel carriers. These are useful for layered sounds, organs, pads, wide harmonic structures, and sounds where several tone components should be heard at the same time. Some algorithms combine parallel carriers with serial modulation chains.

Algorithms with feedback can create sharper attacks, stronger upper harmonics, growling tones, noise-like edges, or unstable digital textures. Feedback is powerful, but it should be handled carefully because small changes can produce large spectral changes.

When reading an algorithm, first look for the operators that reach the output. These are the carriers. Then follow the operators above or connected into them. These are modulators. A good FM programming method is to start with one carrier, then add one modulator, then gradually add more operators only when the sound needs more complexity.

Ratio Mode

In ratio mode, an operator follows the played pitch. A ratio of 1.00 follows the fundamental pitch. A ratio of 2.00 plays one octave above. A ratio of 0.50 plays one octave below. Ratios such as 3.00, 4.00, or 5.00 create harmonic relationships that can still feel stable and musical.

Ratio mode is the normal choice for pitched instruments such as electric pianos, basses, leads, organs, plucks, and pads. When carriers and modulators use simple ratios, the resulting sidebands usually remain connected to the played note.

Fixed Frequency Mode

In fixed frequency mode, an operator uses a fixed frequency in Hz instead of following the played pitch. This is useful for bell tones, metallic hits, noise-like attacks, percussion layers, static modulation, and special effects. A fixed-frequency modulator can create a very different response from a pitch-tracking modulator because its relationship to the played note changes across the keyboard.

Fixed-frequency operators are especially useful as modulators. They can add a constant metallic colour, a fixed buzz, a percussive strike component, or an inharmonic layer. Used carefully, this can make FM sounds less static and more physical. Used heavily, it can quickly become noisy or harsh.

The fixed-frequency controls follow the current DEXZ frequency system, including octave-style fixed frequency ranges. This makes fixed mode useful both for DX-style patch conversion and for direct sound design.

Waveforms

Classic FM synthesis is often based on sine waves, but F_DEXZ allows operators to use different waveforms. A sine wave gives the cleanest and most traditional FM response. It is the best starting point for classic electric pianos, bells, basses, and precise FM programming.

Other waveforms already contain additional harmonics before modulation takes place. This means they can make the result brighter, richer, more aggressive, or more complex. A non-sine modulator can create a much denser spectrum than a sine modulator at the same level.

Use brighter waveforms carefully. They are excellent for aggressive basses, digital leads, harsh textures, and noisy attacks, but they can become too dense very quickly. If a sound becomes uncontrolled, return some operators to sine waveforms and reduce modulator levels.

Operator Level

Operator level is one of the most important controls in FM synthesis. For carriers, level mostly controls loudness. For modulators, level controls modulation depth and therefore timbre. A small increase in modulator level can add brightness. A larger increase can create metallic sidebands, distortion-like behaviour, or noise-like spectra.

When programming FM, do not treat all operator levels like mixer faders. A modulator level is closer to a harmonic intensity control. If the sound is dull, increase the level of a modulator. If the sound is harsh, reduce modulator levels before reducing the final output level.

Keyboard Scaling

Each operator includes keyboard scaling. Keyboard scaling changes the operator level depending on how far the played note is from a selected center point. In F_DEXZ this scaling works around the center point: the center is the reference note where the operator keeps its normal level, and the scaling gradually reduces the operator level on one side of that center.

The KBD amount control is bipolar. Positive values scale the operator down for notes above the center point. Negative values scale the operator down for notes below the center point. At zero, keyboard scaling has no effect. Higher scaling amounts make the level fall away more strongly as the played note moves farther from the center.

This is especially important in FM synthesis because operator level does not only affect loudness. For carriers it mostly changes volume across the keyboard. For modulators it changes brightness, bite, metallic detail, or harmonic complexity across the keyboard. This makes keyboard scaling useful for keeping high notes from becoming too bright, making low notes less heavy, or shaping how a patch changes over the keyboard range.

The center point can be edited per operator. Hold Shift while clicking the KBD control to reveal the center control. Adjust the center value, then hold Shift and click the center control again to return to the normal KBD amount control.

Small scaling amounts are usually best for natural correction. Stronger scaling can be used creatively to make an operator fade out above or below a chosen register, creating split-like timbral behaviour, register-dependent brightness, or different FM character across the keyboard.

Operator Envelopes

Each operator has its own envelope. This is one of the most important parts of F_DEXZ. In FM synthesis, envelopes do more than shape volume. Carrier envelopes shape loudness over time. Modulator envelopes shape timbre over time.

A fast modulator envelope can create a bright attack that quickly fades into a softer sustain. This is the basis of many classic FM electric piano and plucked sounds. A slow modulator envelope can make a pad gradually become brighter or more complex. A delayed modulator can make a second harmonic layer appear after the note has already started.

The small envelope editor shows a compact overview of each operator envelope directly in the operator section. Points can be dragged to change level and timing. Higher points create stronger operator output. Longer horizontal distances create slower transitions. The envelope shape can be used for short percussive transients, sustained tones, evolving pads, delayed movement, and complex layered articulation.

Big Envelope Editor

F_DEXZ includes a larger Big Envelope Editor for more accurate editing of operator and LFO envelopes. Double-click the background area of an operator envelope or LFO envelope to open the Big Envelope Editor. The editor opens on the envelope that was double-clicked and displays a larger time-based view for precise editing.

The Big Envelope Editor is not only a magnified copy of the small envelope display. The small envelope displays are compact shape previews, while the Big Envelope Editor is intended for accurate timing, level editing, comparison, and long envelope work. This is especially useful for slow pads, evolving FM patches, delayed modulators, long LFO fades, imported patches that need correction, and situations where exact timing matters.

The editor contains tabs for OP1 through OP6 and LFO1 through LFO3. Selecting an operator tab shows that operator envelope. Selecting an LFO tab shows the selected LFO envelope. Operator tabs follow the carrier/modulator colour system: carriers are shown in the carrier colour and modulators in the modulator colour. LFO tabs use separate LFO colours, making it easier to see which envelope is currently being edited.

When an operator envelope is selected, optional overlay display can show the other operator envelopes as transparent ghost curves for comparison. When an LFO envelope is selected, the overlay can show the other LFO envelopes. Operator and LFO envelopes are not mixed together in the overlay. Use the OVR button to switch ghost overlays on or off.

The Big Envelope Editor uses a real time scale. This means long envelope stages are shown according to their actual timing instead of being compressed into the same visual width as short stages. This makes it easier to set accurate delayed attacks, long fades, slow evolving modulation, and envelope segments that last many seconds. Because the Big Envelope Editor uses a real time view, it may not always look identical to the compact small envelope preview.

The grid shows time and level reference lines. The horizontal grid uses time labels so that envelope position can be read in musical or practical timing terms. The vertical grid shows level values in volts. The lower information area shows three lines: POS for the absolute time position of the envelope points, LVL for the point levels, and DUR for the delay and stage durations.

The X+ and X- buttons zoom the time axis. Use X+ to zoom in for detailed timing edits. Use X- to zoom out. The Y+ and Y- buttons zoom the level axis. Drag the empty background of the Big Envelope Editor to pan through the visible time and level range. This allows very long envelopes to be edited without forcing the entire envelope to fit into the visible window.

The FIT button adjusts the Big Envelope Editor view so the current envelope fits in the window. This is useful after editing long segments, switching to a different envelope, or losing the active envelope outside the visible range. The RST button resets the Big Envelope Editor zoom and scroll view. It does not reset the envelope shape itself.

Editing in the Big Envelope Editor is direct and realtime. Dragging a point changes that point's timing and level and the result is immediately audible. Dragging the delay handle changes the envelope delay. Hold the fine-adjustment modifier while dragging for more precise movement. Double-click a point to enter exact values numerically. Double-click the delay handle to enter an exact delay time.

Use the Big Envelope Editor when a small envelope display is too cramped or when exact timing matters. For fast visual editing the small envelopes remain useful. For precise sound design, matching operators, setting delayed modulation, comparing envelopes, and working with long time values, the Big Envelope Editor is the recommended view.

Envelope Delay Block

The envelope editor includes a delay block at the beginning of the envelope. This delay holds the operator back before its envelope starts. This is especially powerful for modulators, because it allows a sound to begin simply and then become more complex later.

A carrier can start immediately while a modulator waits before opening. This can create delayed brightness, late metallic movement, evolving pads, secondary attacks, call-and-response behaviour between operators, or a new layer that appears inside a sustained note.

The delay block is not only for slow sounds. Short delays can create double attacks, delayed clicks, rhythmic articulation, or small transient offsets that make the patch feel more alive.

Envelope Point Editing

Envelope points can be edited visually. Dragging a point changes the timing and level of that stage. This makes envelope editing fast and direct, especially when shaping modulator behaviour by ear.

Hold Command on macOS or Control while dragging an envelope point for fine adjustment. Fine adjustment makes smaller movements possible when exact timing or level changes are needed. This is useful for correcting small envelope jumps, matching operators, editing imported DX-style patches, or making subtle changes to modulator movement.

Double-click an envelope point to edit its value numerically. The envelope delay block can also be double-clicked to enter an exact delay value. This is useful when creating precise delayed attacks, matching several operators, or correcting imported patch timing.

For best results, edit carriers and modulators differently. Carrier envelopes should usually define the musical volume shape. Modulator envelopes should define brightness, attack detail, metallic movement, or spectral evolution.

Keyboard and Mouse Shortcuts

- Envelope points can be dragged directly with the mouse.
- Drag the empty background of the Big Envelope Editor to pan the visible envelope view.
- Use X+ and X- in the Big Envelope Editor to zoom the time axis.
- Use Y+ and Y- in the Big Envelope Editor to zoom the level axis.
- Use FIT to fit the current envelope into the Big Envelope Editor view.
- Use RST to reset the Big Envelope Editor zoom and scroll view.
- Use OVR to show or hide transparent envelope overlays for comparison.
- Hold Command on macOS or Control while dragging for fine-tuning.
- Double-click an envelope point to enter a precise value.
- Double-click the delay block or delay handle to enter a precise delay time.
- Double-click the background of an operator or LFO envelope to open the Big Envelope Editor.
- Use Shift + Alt to copy envelope data and
- Alt-click to paste it, where supported by the envelope editor.
- Hold Shift while clicking a KBD control to reveal or hide the keyboard scaling center control for that operator
- Hold Shift while clicking an LFO Speed control to reveal or hide the LFO Sync control for that operator.

Feedback

Feedback sends part of an operator signal back into itself or into a feedback path defined by the algorithm. Small amounts of feedback add brightness, edge, and animation. Larger amounts can create growling tones, distortion-like behaviour, noisy attacks, or unstable spectra.

Feedback is very useful for basses, bells, electric piano bite, metallic percussion, and aggressive digital sounds. It should be adjusted carefully. If a sound becomes too sharp, distorted, or unstable, reduce feedback first, then reduce modulator level if needed.

Global Feedback

In addition to operator feedback behaviour, F_DEXZ includes global feedback control. Global feedback can intensify the overall FM structure and make the selected algorithm feel more animated, aggressive, or unstable.

Global feedback is useful for strong digital basses, metallic impacts, distorted FM leads, experimental drones, and harsh textures. For clean electric pianos or soft pads, use it sparingly.

Polyphony

F_DEXZ is designed as a playable polyphonic FM instrument. Each played note uses its own voice structure so that envelopes, operator phases, and voice behaviour can respond musically to performance.

Polyphonic FM can become dense quickly because every note may contain six active operators, feedback, modulation, and stereo behaviour. If the sound becomes too crowded, reduce operator levels, simplify the algorithm, reduce feedback, or lower stereo spread.

Using DEXZ In Voltage Modular

The easiest way to use F_DEXZ is to connect a polyphonic MIDI source to the three polyphonic input jacks at the top of the module.

A typical setup is:

• MIDI Poly PITCH → DEXZ PITCH
• MIDI Poly GATE → DEXZ GATE
• MIDI Poly VELOCITY → DEXZ VELO
• DEXZ OUT L → Mixer Left
• DEXZ OUT R → Mixer Right

Pitch Bend, Sustain Pedal and Modulation Wheel information are automatically received from the connected polyphonic controller source when supported by the MIDI-to-CV module.

For the best experience, use a polyphonic MIDI source rather than separate monophonic pitch and gate generators.

Polyphonic Inputs

F_DEXZ receives note information through the three polyphonic input jacks located at the top of the module.

• PITCH receives the polyphonic pitch CV.
• GATE receives note on/off information.
• VELO receives note velocity information.

These three signals are normally provided by a polyphonic MIDI-to-CV module such as MIDI Poly or any compatible polyphonic controller module inside Voltage Modular. Connect the three outputs of the MIDI source directly to the corresponding PITCH, GATE and VELO inputs of F_DEXZ.

Sustain Pedal

F_DEXZ supports sustain pedal information from the incoming polyphonic controller stream. When sustain is active, note releases are held until the sustain pedal is released. Operator envelopes continue to behave according to normal sustain pedal operation.

Pitch Bend

Incoming pitch bend data is automatically applied to all active voices. Pitch bend affects operators that follow keyboard pitch in Ratio mode. Fixed-frequency operators remain at their programmed frequencies and therefore react differently during bends.

Modulation Wheel

The modulation wheel is available as a source inside the modulation matrix. By default the modulation wheel does not force a specific destination. Instead it can be routed to any supported modulation target.

Typical uses include vibrato depth, operator level modulation, feedback control, stereo movement, LFO depth, brightness control and evolving FM textures.

UNI and Poly UNI Behaviour

UNI-style operation stacks voices to create thicker, wider, and more animated sounds. Instead of one plain voice per note, multiple voice layers can be used to create weight, detune, stereo spread, and movement.

UNI is useful for large basses, wide leads, animated pads, and modern digital textures. Poly UNI allows this stacked behaviour to be used polyphonically, creating very large FM sounds. Because FM already creates complex spectra, UNI should be used with attention to level and stereo width.

Drift and Spread

Drift adds small pitch or behaviour variations between voices or layers. Spread creates stereo width and separation. Together, these controls can make FM sounds feel less static and more organic.

Small amounts of drift are useful for pads, electric keys, and layered sounds. Larger drift values can create chorusing, instability, or experimental movement. Spread is useful for wide textures, but for strong bass sounds it is usually better to keep the stereo image narrower.

LFO System

F_DEXZ includes internal LFO modulation for movement and animation. LFOs can be used for vibrato, tremolo, timbral movement, stereo motion, feedback changes, operator level modulation, and evolving textures.

Smooth LFO shapes are useful for musical movement such as vibrato or slow pad animation. Sharper or stepped shapes can create rhythmic, digital, or sample-and-hold style movement. Sample and Hold behaviour is useful for random stepped modulation, unstable digital textures, and animated experimental patches.

LFO speed and depth should be adjusted carefully when routed to FM parameters. Modulating pitch produces familiar vibrato. Modulating operator level changes the harmonic content. Modulating feedback can create strong spectral movement. Modulating stereo parameters can create motion without changing the core tone too much.

Host Synchronization

Each LFO can operate either in free-running frequency mode or in host-synchronized mode. The mode is selected directly from the LFO speed control.

Hold Shift and click the Speed control to toggle between Speed and Sync mode. In Speed mode, the control adjusts the LFO frequency in Hertz. In Sync mode, the control selects musical time divisions that are synchronized to the host tempo.

When synchronization is enabled, the LFO speed is locked to the current host tempo and follows the DAW transport timing.

Instead of setting the speed in Hertz, the LFO uses musical time divisions. This makes it possible to create modulation that remains rhythmically aligned with the project tempo regardless of BPM changes.

Typical synchronized values include whole notes, half notes, quarter notes, eighth notes, dotted values, triplets, and faster rhythmic subdivisions. Slow synchronized settings are useful for evolving pads, gradual stereo movement, and long timbral changes. Faster settings can create rhythmic tremolo, stepped modulation, pulsing textures, sequencer-like movement, or tempo-locked FM effects.

When the host tempo changes, synchronized LFOs automatically adjust their rate to maintain the selected musical division. This allows modulation patterns to stay perfectly aligned with the song without requiring manual adjustment.

Host synchronization is especially useful when modulating operator levels, feedback, stereo width, panning, effects, pitch, or other parameters that benefit from rhythmic interaction with the music.

Free-running mode remains useful when a modulation source should evolve independently from the song tempo. This can create natural movement, drifting textures, subtle animation, or modulation relationships that continuously change against the rhythm of the track.

Each of the three LFOs can use its own synchronization setting, allowing a combination of tempo-locked rhythmic modulation and independent free-running movement within the same patch.

LFO Envelopes and Delayed Modulation

F_DEXZ can use envelope-style behaviour for modulation movement. This allows vibrato, timbral modulation, or stereo movement to appear after the note starts instead of being present immediately.

This is useful for expressive sounds. For example, a note can start clean and then develop vibrato after a short delay. A pad can begin softly and slowly gain harmonic motion. A lead sound can have a stable attack and become animated during the sustain. LFO envelopes can also be edited in the Big Envelope Editor by opening an LFO envelope or by selecting one of the LFO tabs in the editor.

Global ADSR Modulation Source

F_DEXZ provides three independent modulation envelopes named ENV1, ENV2 and ENV3. These envelopes can be used individually as modulation sources in the modulation matrix, allowing each envelope to control different parameters with its own timing and shape.

In addition to the individual envelope sources, F_DEXZ also provides a Global ADSR source. Global ADSR is not a separate envelope. Instead, it combines the outputs of ENV1, ENV2 and ENV3 into a single modulation signal. The three envelope outputs are summed and then limited to the normal modulation range.

This makes Global ADSR useful when several modulation envelopes should work together to create one overall modulation shape. For example, ENV1 can provide an initial attack movement, ENV2 can create a delayed rise, and ENV3 can add long-term evolution. The Global ADSR source then represents the combined result of all three envelopes.

Modulation Matrix

F_DEXZ includes assignable modulation routing. Modulation sources can be routed to synthesis targets such as operator level, pitch-related parameters, feedback, stereo behaviour, LFO-related parameters, or other internal controls depending on the available target list.

Each modulation route has a target and an amount. Positive amounts move the target in one direction. Negative amounts invert the modulation. This allows subtle expression, performance control, animated patches, and extreme modular sound design.

External CV modulation is especially powerful in FM, but it should often be used subtly. A small CV change to a modulator level can dramatically change the sound. A small change to feedback can turn a clean patch into an aggressive one. A small change to fixed-frequency modulation can create large timbral shifts.

CV and Modular Use

F_DEXZ is designed for modular workflow. External CV can become part of the FM structure instead of only controlling pitch or volume. Sequencers, envelopes, LFOs, random sources, pressure controllers, and performance tools can all be used to animate the patch.

Because FM responds strongly to modulation, subtle CV amounts are often more useful than extreme modulation. If a patch becomes chaotic too quickly, reduce modulation depth, simplify the algorithm, or use modulation on carrier level and stereo parameters before using it on feedback or deep modulator levels.

External Source Inputs (SRC1 and SRC2)

DEXZ includes two external audio source inputs named SRC1 and SRC2. These inputs allow audio signals from other Voltage Modular modules to become part of the DEXZ FM synthesis engine. External oscillators, wavetable generators, additive synthesizers, samplers, drum modules, noise generators, physical modeling modules, or even another DEXZ instance can be connected and used inside the FM network.

Assigning a Source

SRC1 and SRC2 appear as modulation sources inside the modulation matrix. To assign an external source to an operator, connect an audio signal to SRC1 or SRC2, then create a modulation assignment using SRC1 or SRC2 as the source and an OPx SRC target as the destination. For example, connecting an oscillator to SRC1 and assigning SRC1 to OP2 SRC replaces the internal oscillator of Operator 2 with the incoming SRC1 audio signal.

How SRC Operators Work

When an operator uses SRC1 or SRC2, the operator no longer generates its own internal waveform. Instead, the incoming external audio becomes the signal source for that operator. The external source is then processed by the operator envelope, level control, velocity scaling, keyboard level scaling, algorithm routing, and output panning exactly like a normal operator.

SRC Indicator

When an operator is using SRC1 or SRC2, a highlighted frame appears around that operator's level control. This visual indicator shows that the operator is currently using an external audio source instead of its internal oscillator. Operators without the SRC frame continue to use their normal internal oscillator.

Controls That Continue To Work

• Envelope
• Operator Level
• Velocity Scaling
• Keyboard Level Scaling
• Algorithm Routing
• Panning

Controls That Do Not Affect SRC Operators

• Ratio
• Fixed Frequency
• Fine Tune
• Detune
• Waveform Selection
• Phase Offset
• Operator Feedback
• Pitch-related LFO modulation
• Oscillator-specific modulation targets

The reason for these limitations is that the internal oscillator is bypassed when SRC mode is active. DEXZ receives an already existing audio signal rather than generating a new waveform internally, so oscillator-specific controls are no longer available.

Using SRC Sources As Modulators

The most effective use of SRC operators is usually as FM modulators rather than carriers. An external oscillator or synthesizer can replace a modulator operator and influence the spectrum of a carrier operator through the selected FM algorithm. This makes it possible to create timbres that are impossible with traditional DX-style FM synthesis.

Examples

• Wavetable oscillator → SRC1 → OP2 SRC → OP2 modulates OP1
• Additive synthesizer → SRC1 → OP4 SRC → OP4 modulates a carrier stack
• Second DEXZ instance → SRC2 → OP6 SRC → OP6 becomes part of a different FM algorithm
• Noise source → SRC1 → Modulator operator → Carrier operator for noisy, breathy or percussive textures

External source operators should be viewed as external audio operators rather than fully independent internal oscillators. Their strength lies in bringing completely different synthesis methods into the DEXZ FM network while still benefiting from DEXZ envelopes, scaling, routing, and operator level control.

Monophonic and Hybrid Operator Control via MOD Inputs

F_DEXZ does not use separate dedicated monophonic pitch and gate input jacks. Instead, monophonic control is handled through the assignable MOD inputs and MOD matrix targets.

This allows DEXZ to operate not only as a normal polyphonic FM synthesizer, but also as a modular monophonic voice, a hybrid mono/poly FM structure, or a partially externally sequenced operator network.

MOD inputs can be assigned to global mono pitch CV, global mono gate, individual operator mono pitch control, individual operator mono gate control, or grouped operator mono control such as OP1-2, OP1-3 or OP3-4.

Global Monophonic Mode

Assigning MOD targets to global Mono Pitch CV and Mono Gate turns DEXZ into a fully monophonic modular FM voice.

A typical setup is:

• Pitch sequencer CV → MOD input assigned to Mono Pitch CV
• Gate sequencer → MOD input assigned to Mono Gate
• DEXZ OUT L / OUT R → mixer or effects

Hybrid Mono/Poly Operator Routing

DEXZ can also combine monophonic and polyphonic behavior inside the same FM algorithm. Specific operators can receive monophonic pitch CV and/or monophonic gate control while the remaining operators continue to respond to the normal polyphonic PITCH, GATE and VELO inputs.

Examples include OP1-2 receiving monophonic sequencer pitch and gate while OP3-6 remain polyphonic, OP3-4 receiving monophonic gate only while retaining polyphonic pitch, one operator acting as a monophonic modulator while polyphonic carriers continue normally, or external sequencers driving only selected parts of the FM structure.

Mono Gate and Mono Pitch Can Be Used Independently

Mono Gate and Mono Pitch assignments are independent from each other. Mono Gate only allows external gate timing with original polyphonic pitch. Mono Pitch only allows externally controlled pitch while still using polyphonic gate behaviour. Mono Gate and Mono Pitch together create fully monophonic operator behaviour.

UNI Mode

The monophonic MOD routing system can also be combined with UNI mode. In that case, a single incoming monophonic pitch and gate source can drive stacked unison FM sounds for thicker basses, wider leads, drones or layered modular textures.

Polyphonic Playing

For normal polyphonic playback, use the dedicated polyphonic PITCH, GATE and VELO inputs. The MOD system extends DEXZ with additional monophonic and hybrid modular routing possibilities beyond standard FM synthesizer behavior.

Character / DX DAC Section

F_DEXZ includes an optional Character section that can introduce vintage-style digital coloration inspired by early FM synthesizer hardware. Instead of functioning as a simple distortion or bitcrusher effect, the Character engine subtly reshapes the output stage of the synthesizer to add grit, asymmetry, digital roughness, waveform widening, and additional harmonic complexity.

The Character system operates at the final stereo output stage of the synthesizer, after the FM operators, algorithm routing, stereo mixing, and master processing. This approach preserves the internal FM behavior while adding coloration similar to the imperfect digital-to-analog conversion stages found in early digital synthesizers.

Character Modes

• Clean — Bypasses the Character processing completely and outputs the modern high-resolution DEXZ signal path.
• DX DAC — Adds vintage-style digital coloration inspired by early Yamaha FM hardware. This mode introduces subtle waveform reshaping, quantization behaviour, asymmetry, smoothing artifacts, and additional upper harmonics.
• Dirty — A more aggressive digital coloration mode with stronger harmonic enhancement, rougher quantization behaviour, increased edge definition, and more pronounced spectral expansion.

Character Amount

The Character Amount control determines how strongly the selected Character mode affects the signal. Lower values add subtle vintage coloration and slight harmonic enhancement, while higher values increase waveform reshaping, spectral density, digital roughness, and perceived grit.

Important Notes

• The Character section is inspired by the behavior of early FM synthesizer DAC and output stages, but it is not intended as a mathematically exact emulation of any specific Yamaha DX-series converter.
• The goal is to recreate the musical feel, coloration, and imperfect digital texture associated with vintage FM hardware while remaining flexible and musically useful inside a modern modular environment.
• The effect becomes significantly more noticeable when using high feedback values, complex modulation routings, or strong operator modulation depths.
• Character processing affects the final stereo signal only and does not alter the internal FM algorithm structure.

Stereo Engine

F_DEXZ includes stereo behaviour for widening, layering, and spatial movement. Stereo spread can make operators, voices, or stacked layers feel wider and more animated. This is especially useful for pads, bells, evolving digital textures, atmospheric sounds, and UNI patches.

For bass sounds, keep the stereo image narrower to preserve weight and focus. For pads and drones, wider settings can create space and movement. For leads, moderate spread can make the sound larger without losing clarity.

Audio Outputs

F_DEXZ provides stereo audio outputs.

• OUT L is the left audio output.
• OUT R is the right audio output.

Connect both outputs to a mixer, audio interface, effects chain or recorder for full stereo operation. If only OUT L is connected, the synthesizer can still be used in mono.

DX7 SysEx Import

F_DEXZ can import DX7-style SysEx patch data and translate it into the DEXZ engine. This makes it possible to explore classic FM patch banks inside a modern modular environment.

DX7 import should be understood as patch conversion, not always perfect cloning. The original DX7 has its own operator scaling, envelope behaviour, feedback response, frequency handling, and output character. F_DEXZ translates the important patch information into its own architecture, but some patches may need adjustment after import.

If an imported patch sounds too harsh, reduce modulator levels, reduce feedback, or adjust operator envelopes. If it sounds too dull, increase modulator level or check whether frequency ratios and fixed-frequency settings converted as expected. If the attack feels wrong, inspect the modulator envelopes first, because most of the recognizable DX-style attack character comes from modulator envelope behaviour.

DX7 Patch Browser

Clicking the DX7 file selector opens the DX7 Patch Browser. The browser displays all patches found in the loaded DX7 bank and allows immediate auditioning and loading of individual sounds.

When a DX7 patch is loaded, all six operators are automatically switched back to sine-wave mode. This ensures that imported patches reproduce the intended DX-style FM structure.

Custom DrawWave, Table, or External Oscillator waveforms already loaded into operators are not erased. Only the active waveform selection is reset. You can switch any operator back to a custom waveform source at any time after loading a DX7 patch.

DX7 Compatibility Notes

Classic DX patches often rely on very specific operator level scaling and envelope response. Even small differences in level mapping can make a patch sound too bright, too noisy, too soft, or too clean. This is normal when translating between FM engines.

Fixed-frequency operators are especially important for metallic and percussive DX patches. LFO speed, feedback behaviour, and operator scaling may also need small corrections after import. Treat imported patches as strong starting points that can be edited further inside DEXZ.

Building a Sound

A reliable way to build a patch is to start with one carrier operator. Set its level and envelope so that the basic volume shape works. Then add one modulator. Adjust the modulator ratio, level, and envelope until the attack and brightness feel right.

After that, add more operators only when needed. FM can become complex very quickly. A strong patch often uses fewer operators than expected. The best results usually come from clear relationships between carrier level, modulator level, envelope timing, frequency ratio, and algorithm structure.

When a patch becomes too harsh, do not immediately lower the final output. First reduce modulator levels, feedback, or bright waveforms. When a patch is too dull, increase modulator level, raise its envelope, choose a brighter waveform, or add a small amount of feedback.

Classic Electric Piano Approach

For electric piano sounds, use a carrier with a natural decay and one or two modulators with quick attacks and shorter decays. The modulator should be strong at the start of the note and then fade back. This creates the familiar bright strike followed by a warmer body.

Start with simple ratios such as 1.00, 2.00, or 3.00. Add a small amount of feedback if more bite is needed. Keep operator levels controlled to avoid harsh peaks. If the sound is too synthetic, use subtle drift or stereo spread.

Bell and Metallic Sounds

For bells, use higher ratios, unusual ratios, or fixed-frequency modulators. Longer decay times help create ringing tones. A carrier can remain simple while modulators create the metallic structure.

Feedback can add brightness and complexity, but too much feedback can turn a bell into noise. Slight detuning, fixed-frequency modulation, and long modulator decays can make bell sounds more realistic and less static.

Pads and Evolving Textures

For pads, use slower envelopes, delayed modulators, stereo spread, and gentle LFO movement. The delay block is especially useful for pads because it allows harmonic layers to appear after the note begins.

Let the carrier start smoothly, then allow one or more modulators to enter later. Use slow LFO modulation on operator levels, spread, or feedback for evolving movement. Keep modulation amounts moderate if the sound should remain musical.

Basses and Leads

For basses and leads, use stronger modulation and tighter envelopes. Short attack times and controlled decay stages help create punch. Feedback can add aggression, but output level and low-frequency stability should be watched carefully.

For bass patches, keep stereo spread narrow and avoid excessive fixed-frequency low modulation unless the effect is intentional. For leads, moderate UNI, drift, and feedback can create strong modern FM tones.

Metallic Percussion

For metallic percussion, use fixed-frequency modulators, high ratios, short carrier envelopes, and fast modulator decays. Feedback can add noise and impact. A delayed or very short modulator envelope can create a click, strike, or metal hit at the start of the sound.

Try building percussion from a simple carrier and one strong modulator first. Then add additional modulators only for extra metallic detail or tail movement.

Using Delay Creatively

The envelope delay block can create delayed attacks, secondary transients, evolving modulation, rhythmic articulation, and call-and-response behaviour between operators.

A carrier can sound immediately while a modulator appears later. Another operator can add a short delayed click or metallic edge. With longer held notes, delayed modulators can make the sound feel alive instead of static.

Advanced Sound Design

Advanced FM programming often comes from controlling contrast. A clean carrier with a short bright modulator creates a pluck. A slow carrier with delayed modulators creates evolving pads. A fixed-frequency modulator with feedback creates metallic or noisy structures. A stacked UNI patch with spread and drift creates wide modern digital textures.

Do not add complexity everywhere at once. Choose where the complexity should happen: attack, sustain, release, stereo field, feedback, or modulation movement. This makes the patch easier to control and more musical.

Troubleshooting

If the sound is silent, check whether at least one carrier operator is active in the selected algorithm. Also check carrier level, carrier envelope level, final output level, and whether the operator is switched on.

If an operator seems to do nothing, it may be a modulator that only affects another operator. Increase the level of the carrier it feeds into, or choose a simpler algorithm to test the operator.

If the sound is too harsh, reduce modulator levels, reduce feedback, use simpler ratios, or switch some operators back to sine waveforms. If the sound is too dull, increase a modulator level, raise its envelope, choose a brighter waveform, or add a small amount of feedback.

If imported DX7 patches sound wrong, inspect operator levels, fixed-frequency settings, feedback, and envelopes. Most conversion differences come from level scaling, envelope timing, feedback response, or fixed-frequency interpretation.

If the sound clips or becomes unstable, reduce operator levels before reducing only the final output. FM overload often starts inside the modulation structure, not only at the final output stage.

Performance Tips

Use simple algorithms for clear, playable sounds. Use complex algorithms for evolving textures, metallic tones, and experimental sounds. Keep bass patches narrower in stereo. Use wider spread for pads, bells, and atmospheric patches.

When using UNI or Poly UNI, watch the level carefully. Stacking voices makes the sound larger, but it also increases spectral density and output energy. Reduce operator levels, feedback, or spread if the patch becomes too heavy or unfocused.

For expressive playing, route modulation to operator levels, feedback, vibrato amount, or stereo spread. These targets often feel more musical than simply modulating final volume.

Summary

F_DEXZ is a deep six-operator FM synthesizer for classic digital tones, DX-style patch exploration, and modern modular sound design. Its strength lies in the combination of algorithm-based FM routing, editable operator envelopes, delayed envelope starts, waveform choice, feedback systems, internal LFO movement, stereo behaviour, UNI stacking, assignable modulation, detailed Big Envelope editing, and DX7 SysEx import.

The most important idea is simple: carriers control what you hear directly, while modulators control how the tone changes. In FM synthesis, envelopes and operator relationships shape timbre as much as pitch and level. By controlling carriers, modulators, ratios, envelopes, feedback, and stereo movement carefully, F_DEXZ can move from clean classic FM to evolving digital landscapes, metallic percussion, expressive keys, animated drones, aggressive basses, and experimental modular textures.

UPDATES
Build 64 - Level Scaling and Algorithm Feedback corrected.
Build 66 - Added MONO PITCH CV and MONO GATE as targets.
Build 68 - Character added.
Build 71 - Extra MONO targets included; can now still receive Poly data next to MONO PITCH and MONO GATE, MOD4 input added.
Build 72 - Shift-click LFO speed to set to Sync to Host; polyphony voice changes now handled correctly.
Build 73 - Bug that made LFO change to selected LFO's speed solved.
Build 74 - LFO knob state was not saved; corrected.
Build 75 - Further optimizations.
Build 78 - Added Big Envelope Editor with OP/LFO tabs, real-time scaling, zoom, pan, fit view, ghost overlays, delay editing, point value display and detailed POS/LVL/DUR information.

Build 79 - Added SRC1 en SRC2 input and MOD TARGETS OP1 - 6, so an external source can take the place of an internal OP, although limited - see above. Build 80 - Added outline for OP having an external source. Build 81 - BEE grid ‘density’ changed when zooming out. Build 82 - Mono-mode improved to act like monophonic keyboard (fast trills) Build 83 - Wave import for OPs Build 84 - Copy paste now supports imported waves Build 85 - Popup screen for Mod Source and Target Build 86 - Popup screen for Waves Build 87 - Popup for FILE and PATCH of DX7 import