The 8BitSynth doesn't rely on typical synthesis methods to generate sound. Rather it relies on a virtual 8bit processor evaluating an expression and outputting the result of the expression as audio. Any valid combination of numbers and mathmatical operators can be used to craft the expression, and one variable is permitted: time (t). Because the calculations are done on 8 bits, numbers greater than 256 will wrap to 0, ensuring the signal is always within a certain range. While there are some tricks to getting certain results, this isn't a synth where you set out to produce a particular sound but rather a place to experiment and to be surprised by what you create. Because the output is 8 bit, this synth produces somewhat distorted sounds suitable for chiptunes, dubstep or experimental electronica. The 8BitSynth 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. 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 as well as samples used. To load a preset, touch the preset LCD. This will bring up a list of saved presets to choose from. To scroll between presets in a directory, swipe left or right on the preset LCD.
  3. 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/padsynth.
  4. Note On LED: This LED lights up whenever a note is triggered.
  5. A-B Blend knob: This knob controls the output mix between expression A and expression B
  6. Octave knob: Coarse frequency tuning for the expression evaluator, from -4 to +4 octaves.
  7. Semis knob: Frequency tuning for the expression evaluator, in semitones (regular notes on a keyboard)
  8. Cents knob: Fine frequency tuning for the expression evaluator, in cents. 
  9. Output Volume knob: The final output volume of the PCMSynth.
  10. Output VU meter: Indicated the level at which the PCMSynth is outputing signal. If this reaches RED, then the PCMSynth will output distorted sound.
  11. Expression window: This is where your expression is displayed. Touching once inside the expression window places the cursor at the touched location. Long-pressing the expression window will offer to copy the content of the other expression into the one currently selected.
  12. Expression selection switch: Selects which expression is displayed in the expression window and which expression is edited.
  13. Expression programming keyboard: Contains various digit and operator keys as well as the time variable key (T), parentheses, and a backspace key ( < ). Operators:
    • ^  Bitwise exclusive OR (XOR). For each bit, result is 0 if both sides are 1 or 0, and result is 1 otherwise.
    • & Bitwise AND. For each bit, set to 1 only if the numbers on both sides are 1
    • |  Bitwise OR. For each bit, set to 1 if one the numbers on either sides is 1
    • << Shift left. Shifts all bits to the left by the amount specified (equivalent of multiplying by powers of 2)
    • >> Shift right. Shifts all bits to the right by the amount specified (equivalent of dividing by powers of 2)
    • + Standard arithmetic addition.
    • - Standard arithmetic subtraction.
    • * Standard arithmetic multiplication.
    • / Standard arithmetic division.
    • % Modulo (aka remainder) part of a division
    • ( and ) Parentheses, used to force the order of evaluation.
  14. 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.
  15. Preview Keyboard: This keyboard is used to play notes to help when designing sounds with the PCMSynth.
  16. Octave buttons: Raises or lowers the octave of the Preview Keyboard.