The definitive MIDI controller

What is RPC?

The Raspberry Pi Controller is intended to be a stand-alone MIDI sequencer workstation, made with open-source software and DIY electronic components. It is built around a Raspberry Pi board delivering a solid user interface. The I/O connections are served by an Arduino feeding directly to four MIDI inputs and outputs, guaranteeing accurate timing.

The name pays homage to the venerable Akai MPC series, but this is going to be a whole new kind of beast.

If this project is of interest to you, or if you would be interested in having your own little RPC (DIY, kit or pre-built, doesn’t matter) please drop me an email, tell me what you want to see me accomplish, and I will add you to the news email list. You’ll be the first to hear of updates, and I will be aware if someone actually wants one! No spam.

The protosynth

The DSP synthesizer project has taken most of my attention lately, with the RPC making steady progress on the background. The unique synthesis algorithms of the synth will make it a beast of a companion for the RPC.

Recent posts


It’s the realtime aspect of games and musical instruments that gives them their universal appeal. People can’t stand tools that do not respond in a timely manner, be it software or hardware.

So what happens then when you take something so profoundly clunky that everyone is accustomed to it, and embed the idea of a realtime feedback loop in it? Your users get to travel freely from one parameter set to another. And they will find it much easier to reach interesting parameter subspaces and their sweet spots.

This alone is often enough to turn a complicated-looking system into a playful toy.

Of course, sometimes you still end up wishing everyone had a supercomputer for the number-crunching.

New sounds, moment of inspiration

A few new sound clips: the first one is another experiment with the oscillator pitch shifting, tuned to sound like inharmonic overtones. Just three oscillators, all parameters are constant. There is no chorus effect, no LFOs, all the movement is coming from the oscillators!

The second one is a very plain goa riff loop, playing with the filter and oscillator waveshape knobs. It starts slow, but once it gets going it’s unstoppable.

The last clip is a repeating bassline (from a game that was very popular in its time, I have to add) with again just one single oscillator producing the sound, with the synth in monophonic mode. Enjoy!

Reverb and delays provided by Lexicon as before.

It’s alive!

The box for the protosynth is finally complete. See the previous posts for details. The paint is still not entirely finished and could use some final touch-up, but it’s good enough for now. First pics!

Sumutor-1 ready to rok

Sumutor-1 ready to rok

All the hardware is in there and, most importantly, it all seems to work. All knobs and buttons register, leds light, and although there is no real gui, you can tap on the mock buttons and they register. Headphone output works, but I’m not sure yet if the voltage levels are right or if it’s clipping. All the parts of the synth work just as before.

The picture is taken at such an angle that the display looks empty. No, it works just fine. The led segment displays will get covered later, I still have to find some nice red film to put on top of them.

Sumutor-1 with its fleshy belly open

Sumutor-1 with its fleshy belly open

All the internals are in place. In the cover: thumbstick, big buttons and the headphone amplifier on the left, with the main UI panel and the touch TFT screen with its SD card slot taking the rest of the space. On the bottom: the synth on the left has grown itself an opamp attachment and a couple of admittedly ugly connectors, the USB+MIDI interface in the middle, and power supply board and the power connector and switch on the right. Oops, I forgot to remove the jtag cables for the photo shoot.

I’ll take some fancier shots and soundclips later (see the previous posts though!). There’s still much to do on the software side.