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MicroDexed (from now called MD) is a FM-(Software-)Synthesizer with six operators and much additional features (like effects and a some extensions). It is written in C/C++ for the microcontroller Teensy-3.6/4.x. The sound generation (msfa) from the free VST-plugin Dexed was used and a user interface was created using two encoders and a LCD display. It is controlled via MIDI (you need a keyboard) and voice presets can also be programmed via MIDI.

Ideally, the software works together with the TMA (TeensyMIDIAudio) hardware or – with changes to the source code – with  the TGA-board or with only a Teensy(-3.6) and a Teensy audio card.


  • Compatible to a legendary FM synth with six operators from a famous Japanese manufacturer
  • MIDI interface:
    • DIN IN/OUT with software THRU (can be disabled, optional hardware THRU possible)
    • USB-Slave (for connecting to a PC)
    • USB-Master (for connecting keyboards)
  • Audio interface:
    • RCA stereo IN/OUT with audio THRU (daisy-chain your sound generators)
  • Onboard effects:
    • Chorus (mono)
    • Delay (mono, up to 500ms, with feedback)
    • Low-pass filter with resonance
    • Reverb (stereo)
    • Resonant low-pass filter
  • Mono sound engine with panorama controller before reverb
  • Up to 20 voices of polyphony
  • Up to 100 banks of 32 voices can be stored on an SD card
  • MIDI SYSEX compatible
    • Sounds can be edited with external editors like…
    • Sending of Voice/Bank MIDI-SYSEX dumps
    • Receiving of Voice/Bank MIDI-SYSEX dumps
    • Voice-Parameter change via MIDI-SYSEX
    • Flexible MIDI controller settings with additional features
    • Modwheel, Pitchbend, Portamento, Breath-Controller, Aftertouch, Foot-Controller
    • Additional modes for most controllers (linear, inverse, direct)
    • Controller parameter change via MIDI-SYSEX
    • Additional MIDI-CCs
      • Bank select
      • Preset select
      • Volume
      • Panorama
      • Filter resonance
      • Filter cutoff
      • Delay time
      • Delay feedback
      • Delay volume
  • Storage of voice presets, effect presets and combinations of both as “performance” on SD card
  • Transpose, fine-tune, mono-mode
  • Note refresh options: normal or retriggered
  • Velocity level adaption
  • Three sound engines:
    • Modern : this is the original 24-bit music-synthesizer-for-android implementation.
    • Mark I : Based on the OPL Series but at a higher resolution (LUT are 10-bits). The target of this engine is to be closest to the real DX7.
    • OPL Series : this is an experimental implementation of the reverse-engineered OPL family chips, 8-bit. Keep in mind that the envelopes still need tuning.
  • Open-Source (

For more information, please take a look at the user manual.

Downloads / Repository

Installation from Arduino-IDE