multi - midi controller/filter/router, sound generator

multi is an open hardware circuit board hosting a Seeeduino XIAO, 6 pots, 2 pushbuttons, 2 Midi DIN connectors and an audio output.
The Seeeduino XIAO board carries a powerful ATSAMD21G18A-MU which is a low-power microcontroller and has 14 GPIO PINs, a DAC output and one UART interface. To avoid grounding loops the MIDI input is properly opto-isolated, as required by official specifications.

You can program multi as you need, using the Arduino IDE.
On the MIDI side, possible use includes advanced midi controlling, filtering and remapping as well as algorhitmic arpeggiators and aleatoric patch generators.
Since the Xiao board has a DAC, multi can also be used to produce sounds using the Mozzi sonification library written by Tim Barrass or accessing directly to the DAC output.

I’m using it along with my DIY norns and they pair very well.

On the multi github repository you can find the fabrication files, the schematic and the software I’ve written so far:

  • drone it’s a six oscillators drone machine.
  • synth_sequencer three oscillators monophonic synth with embedded sequencer. It receives MIDI clock and note messages.
  • bytebeat player allows to play algorithmic music with no instruments and no real oscillators but a math expression that creates an audio output waveform as a function of time, processed 8000 times per second. The expression has six parameters accessible through the multi knobs.
  • midi converter is a USB to 5 DIN bi-directional MIDI converter.
  • midi metronome takes the MIDI clock from the 5 DIN midi connector and generates a metronome click on the audio output, to allow acoustic musicians to synchronize their performance to an electronic setup.
  • hardware test use this software to test your build.
  • blink the ubiquitous blink sketch.

Kits and assembled units are available for purchase, please contact me directly and avoid discussion of buying/selling in this thread. Any comments and suggestion will be appreciated.


I love the look of it!

Are there any sound samples available to listen to?

1 Like



Sweet, thank you - nice work!

Hopefully will drop you a line after next $DayJob paycheck lands…


i have to agree
this is pretty cool!


Sweet, thank you - nice work!

thanks @Helen

this is pretty cool!

thanks @glia

In the videos the knobs are blue (ranging from light to dark), but I like most the “pride edition” as shown in the the last pictures. :rainbow_flag:

I shot a new video showing multi as a four oscillator synth with sequencer.

The sketch is available on github.



If there’s ever a v2 I’d love to see an expansion header for adding additional boards for more control, i/o etc.

This seems like it could be the brain for a really nice DIY MIDI router if there were an option to add more ports and a few more UI elements.

EDIT: basically like how MIDIbox lets you daisychain a few 4x4 I/O boards to add more ports to your project. A barebones DIY MIDI router/filter that could be built with an arbitrary number of ports up to at least 16x16 (or more) is something that I would absolutely jump on.

very interesting, is this similar to using the MIDI host by sevillesoft that allows MIDI communication between computer/ableton and norns?

@0netwo0netwo No, multi has not MIDI host capabilities.
In case of use with norns, you can use it as a midi controller. It has six pots so it goes well with scripts like oooooo :smiley: and in this case it can also be used as sound source for norns.
There’s a sketch that generates sound using the bytebeat technique and sends MIDI CC at the same time, for example:

Multi can also be used as a MIDI converter from USB to DIN, if you need to hook your norns to an old synth with no USB connections.