FM Synth


The FMSynth is a 3-operator modeling synth which uses Frequency Modulation (through a phase modulation algorithm) to produce sound. Each operator is controlled by a separate envelope and there are 5 different ways to combine the operators. The FMSynth tutorial video shows how to use this machine.

UI Reference

  1. Machine label: This is used to identify this machine in various places throughout the app. Its value can be changed via a long-press action (label changes color to indicate a successful touch). Upon successful long-press, a keyboard offering you to rename the machine will appear. Use this to identify a machine in a rack configuration where there might be more than one instance of the same machine.

  2. Note On LED: This LED lights up whenever a note is triggered.

  3. Preset LCD: This display shows the name of the last loaded preset and is used to load presets. A preset is a saved file that contains the positions of all knobs and controls. To load a preset, touch the preset LCD. This will bring up a File Browser with a list of saved presets to choose from.

  4. Save Preset button: This button allows you to save your own presets to disk for use later. Pressing this button will bring up a keyboard allowing you to name your preset. Presets are stored on the external storage in /caustic/presets/fmsynth.

  5. Operator3 Feedback knob: Controls the amount of signal from operator 3 that is fed into itself for modulation

  6. Operator3 Feedback velocity button: When pressed, note velocity affects how much feedback is applied to operator3.

  7. Volume velocity button: When pressed, note velocity affects the output volume of the FMSynth.
  8. Output Volume knob: The final output volume of the FMSynth.
  9. Output VU meter: Indicates the level at which the fmsynth is outputing signal. If this reaches RED, then the fmsynth will output distorted sound.

  10. Algorithm selector: Touch to change, 5 algorithms to choose from. The different algorithms change which operator modulates which other operator(s) and which operators are fed to the output.

  11. LFO target selectors: Press one or multiple buttons to have the LFO affect these parameters. A1 = amplitude of operator 1, A2 = amplitude of operator 2, A3 = amplitude of operator 3, AO = amplitude of the output. F1 = frequency of operator 1, F2 = frequency of operator 2, F3 = frequency of operator 3.
  12. LFO Rate knob: The speed at which the LFO modifies its target value(s).
  13. LFO Depth knob: The amount of modification the LFO applies to its target value(s).
  14. Level knob: The output volume of the operator. In case the selected algorithm has this operator modulating another, this determines the modulation amount. In case the selected algorithm has this operator outputing to final mix, this determines the output volume level in the mix.
  15. Level velocity button: When pressed, note velocity affects the level of the operator.

  16. Octave knob: Coarse frequency tuning for the operator, from -4 to +4 octaves.
  17. Fixed tone button: When pressed, the tone emitted from this operator will be fixed and determined by the octave and semis knob. It will not follow the note played on the keyboard.

  18. Semis knob: Frequency tuning for the operator, in semitones (regular notes on a keyboard)
  19. (ommited)
  20. Volume Envelope Attack knob: The amount of time before the operator reaches the level defined by the level knob, stating at 0.
  21. Volume Envelope Attack Exp button: When selected the attack curve will be exponential instead of linear.

  22. Volume Envelope Decay knob: The amount of time, after the attack period, for the level to go from the level knob value to the sustain level.
  23. Volume Envelope Decay Exp button: When selected the decay curve will be exponential instead of linear.

  24. Volume Envelope Sustain knob: The value for operator level at which to settle, once the attack and decay period have elapsed and the note is held, relative to the level knob.
  25. Volume Envelope Link button: When selected, the values of decay and release will be linked. Any changes to one will reflect in the other.

  26. Volume Envelope Release knob: The amount of time for the level to go from the sustain level down to 0.
  27. Volume Envelope Release Exp button: When selected the release curve will be exponential instead of linear.
  28. Mute/Solo buttons: These buttons link to the ones in the mixer and are used to cut out this machine from the final mix or listen to only this machine.

  29. Polyphony buttons and display: Sets the number of notes which can be active at once. If the requested number of notes exceeds the polyphony count, a voice will be stolen from the oldest playing note.

  30. Preview Keyboard: This keyboard is used to play notes to help when designing sounds with the fmsynth.

  31. Octave buttons: Raises or lowers the octave of the Preview Keyboard.