The Modular Synth is a synthesizer where you can assemble your own synth from components. Components are selected from a catalog, placed and routed. A newly placed modular is empty and contains no components. Touch inside one of the component slots to bring up the component catalog. Output can be either mono or stereo, depending on output routing The Modular tutorial video shows how to use this machine. A lot can be learned by studying the various built-in presets.

UI Reference

Front view

Rear View


  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 a link to all samples used as well as the positions of every knob. To load a preset, touch the preset LCD. This will bring up 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 in /caustic/presets/modular. 

  5. Delete component button: Press this button to select a component to remove. Removing a component clears all wire routing to and from it.
  6. Flip button: This button toggles between front and read view of the modular synth. The front view contains the majors knobs and controls while the rear view is where gain adjustments and wire routings are made.
  7. Preview keyboard button: This button toggles visibility of the preview keyboard for the modular synth. In order to maximize component area, the preview keyboard is not present by default. 
  8. 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.

  9. Output Volume knob: The final output volume of the Modular synth.

  10. Output VU meter: Indicates the level at which the Modular is outputing signal. If this reaches RED, then the Modular will output distorted sound.

  11. Modular component: There are many different types of modular components, each having a particular role in how it treats the signal going through it. 

  12. Component bay: To place components, touch inside one of the component bays and the component catalog will be displayed. Once placed, some components span 1 bay some span 2 bays. If the catalog is brought up on a bay where there is only room for 1, the component catalog will disallow selection on large components.

  13. Preview keyboard gripper: Once, visible (7), the preview keyboard can be moved vertically by dragging this gripper area.
  14. Preview Keyboard: This keyboard is used to play notes to help when designing sounds with the Modular. Toggle its visibility using the keyboard button(7)
  15. Octave buttons: Raises or lowers the octave of the Preview Keyboard.
  16. Note CV signal jack: The note control voltage (CV) is a signal representing the note played. Route this signal to "note" inputs on sound generator components for example.
  17. Note Velocity signal jack: The note velocity is a signal representing the velocity associated with the note played. Normally velocity gets reflected as a change in output volume and if that's all you want, route this signal to the "Volume Mod" input (22). However, because this is a regular control signal it can be routed to filter controls or more creatives uses too.
  18. Mod wheel signal jack: This control signal represents the value of the Modulation wheel on a connected MIDI controller. This signal has no effect without a MIDI controller connected.
  19. Left/Mono output jack: This is the Modular's main audio output (routing to the effects and mixer after volume adjustments). 
  20. Output gain adjustment knob: Used to control the output volume for the modular patch, and leaves the main  Volume knob(9) free for general use and automation.
  21. Right output jack: If a signal is routed to the right output jack, it will be assumed that the synth should output Left and Right signals as part of a stereo output for the synth.
  22. Volume modulation jack: Route a control singal to this input jack to affect the overall volume of the Modular patch's output volume.
  23. Component connection jack: Left-most connection jacks on modular components are generally inputs and thus receive one control signal. Right-most connection jacks are usually outputs and can be routed to one or many inputs by dragging from the output jack to the desired input jack(s).
  24. Routing wire: Wires are automatically placed when a connection is made between an output jack and an input jack(23)