This is my personal cheat sheet for the TD-3-MO. I was building it over months, it is still growing and it is not meant to be complete. If you have questions or suggestions, don't hesitate to drop me a line.

The Behringer TD-3-MO is a Roland TB-303 clone with Devil Fish modification. Find more about the Roland TB-303 here and about the Devil Fish mod here


  • Tune: Tuningof the internal VCO oscillator. Small changes have an impact, always check before playing. When turning it or down all the way, an octave may have not been reached. Tune note A to 220 Hz or note C to 264 Hz. play a C note by switching to Pattern Play and press Write/Next
  • Cutoff: frequency of the low pass VCF filter. Can be fully closed and goes up to 5 kHz (can be fine tuned by opening the box and turning the internal poti, may loose warranty). 3-pol or 18 db/Octave 
  • Resonance: controls the resonance / emphasis singal level at the cutoff frequency. The filter can oscillate itself with high settings 
  • Envelope: controls the amount of the fixed envelope of the filter cutoff frequency (VCF) 
  • Decay: length (volume envelope) of all notes (VCA) 
  • Accent: intensity of notes with accent. Accent affects various parameters, especially shortens Decay of the filter and raises resonance. Notes with velocity > 96 count as accented notes 


  • Soft Attack / Normal /Accent: 2nd envelope for the filter (VCF). Allows different envelopes for normal notes and notes with accent. LEDs below show activity. 
    • Soft Attack: 0,3 to 30 msec (for notes without accent) 
    • Normal decay: 16 msec to 3 s (for notes without accent) 
    • Attack decay: 30 ms to 3 s (for notes with accent) 
  • Filter tracking: controls cutoff frequency by note pitch. Opens the filter for high pitch and closes for low pitch. If resonance is high and oscillators are off, the filter can be played like a sine oscillator. 
  • Overdrive: intensity of the slight distortion. Adds harmonics and bass. Can be used together with volume to adjust the sound. When closed, the normal VCO level is used, so it should always be opened a bit


  • Sub Osc: enables the sub oscillator 
  • Sub Osc Level: level of the sub osc
  • Tempo: the speed of the pattern playback (bpm)
  • Wave: select waveform or mute the main oscillator. When muted, the filter can be played (turn up resonance, check with accent sweep at 1) or the audio input can be filtered. 


  • Slide Time: duration of the slide between 2 notes (portamento) 
  • Sweep Speed: relative time of the accent sweep. It controls the speed of the slide relatively based on note length and tempo
  • Accent Sweep: intensity of the filter accent. It controls the impact of accent on resonance and filter-decay. 0: no accent sweep,1: high resonance, 2: normal.
  • Filter FM: modulation of the filter with fm. AC-coupled Filter FM from the signal of the VCA. Modulates filter-frequency with the outgoing audio signal. Adds harmonics with low settings and distortion with high settings
  • Volume: 😀
  • Muffler: Compression or soft clip distortion that can be used for heavy resonance and cutoff settings. Implemented by driving the VCA with higher level. It lowers high frequencies and keeps bass. Diode based. 
  • Accent: adds accent to all notes, great for fills



Write a pattern 

  1. Pattern Select
  2. Pattern Write
  3. Pattern delete:
    1. Select A or B
    2. Press “Clear” + number of pattern 
  4. Set number of steps:
    1. Function + X * Step button
  5. Writing (order of 1. and 2. can be switched):
    1. Set duration of notes (no audio will be heard):
      1. Time Mode
      2. X * normal / tie / rest (pause) 
      3. When the number of defined steps is reached (16 is default), Time Mode is switched to Normal Mode automatically
      4. Check the timing by go into Time Mode and press Write/Next. It is not possible to change timings, instead you have to re-enter the whole pattern.
    2. Set pitch of notes:
      1. Pitch Mode
      2. X * keyboard
        1. If transposing is required, first press the according transpose button, then the keyboard together
        2. the pauses dont count, dont set them!
      3. Check the melody by go into Pitch Mode and press Write/Next. Change the current note or go back with Back to change the last note
      4. Press Pitch Mode to restart, or Function to exit Pitch Mode
    3. Accent/Slide/Transpose
      1. Pitch Mode
      2. Step through with Write/Next button. Rests don't count (if you have e.g. 3 rests in your 16th note pattern, you end und with only 13 steps)
      3. If Note shall bei edited, keep next pressed and also press Accent/Slide/Transpose
  6. Copy pattern from A to B (the same for copying from pattern 1 to 2):
    1. Write Mode
    2. Choose B
    3. Clear B
    4. Choose A
    5. Function + (Bar) Copy
    6. Choose B
    7. Function + (Bar) Paste
  7. Chain Patterns
    1. While still in Write Mode, press the number of the first pattern on the keyboard and the also click the number of the second pattern


Alternatively press Start/Stop & Clear to generate a random pattern (it creates a variation of the previous pattern) 

Play a pattern

  1. Pattern Select
  2. Pattern Play
  3. Pattern A/B
  4. Transpose live
    1. Pitch Mode + keyboard 



For the MIDI DIN port only Midi clock, Note on/off and cutoff (cc74) is implemented. 

USB MIDI with the USB port enables SysEx. Implemented functions: Note-on/off, All-Notes-off, Filter-Cutoff, Pitchbend, Clock, Start/Stop/Continue



  • For the well known acid sound, use accent, octave jumps and slides
  • when using accent, try to use them in a row as described here
  • Use filter in to filter an external audio signal



  • Changing the sync source: Midi / USB / internal / Trigger: press back + write/next, then press desired sync method on keyboard and resolution (24ppq works for most cases)


© 2024 by joit, 04-21-2024

Joit - drop it like its acid