Mighty Mini MIDI Sequencer

Took me a while to figure out how to get these to play nicely simultaneously.

Reason plays the chords to the External MIDI Instrument, which sends note, gate, and velocity data to my USB MIDI interface. From there to the Sparkfun MIDI-Shield (Spark Electronics), which provides a MIDI-friendly interface to the Arduino “Uno” microcontroller below. A nifty sequencer program (or “sketch”), written in C by Brendan Clarke, detects note changes and generates MIDI note events for the MIDI-Shield to return via its MIDI OUT port. Although I don’t use them here, the Spark interface allows me to adjust tempo and gate length, as well as selecting from among several pre-programmed note sequences. A little tweaking in C and I can modify the sketch for longer sequences than eight notes, to add different patterns, and so on.
Once the MIDI events are received back at my USB interface, they are routed back to a “Combinator” utility module in Reason, where I have assembled three instances of the Malström Graintable Synthesizer. (Yeah, I know: we’re accustomed to seeing Maelstrom, but what the hey!)
As long as I don’t forget to assign the MIDI events to the correct device, I can record an audio track while simultaneously playing the MIDI notes that will be recorded. No issues with latency thus far, but I’m not pushing the envelope that much.