Minimal MPE example for Norns

Engine_MinimalMPE.sc

Engine_MinimalMPE : CroneEngine {
	var synths;

	*new { arg context, doneCallback;
		^super.new(context, doneCallback);
	}

	alloc {
		synths = Array.newClear(8);

		SynthDef("mpeSynth", {
			arg out, freq = 110.0, gate = 1.0, amp = 0.0;
			var sig;
			var env = Env.adsr(0.02, 0.1);
			sig = SinOsc.ar(freq, mul: amp * 0.8 * EnvGen.kr(env, gate, doneAction: Done.freeSelf));
			Out.ar(out, sig!2);
		}).add;
		this.addCommand("noteOn", "if", { arg msg;
			var chan = msg[1];
			if (synths[chan] != nil) {
				synths[chan].set(\gate, 0);
			};
			synths[chan] = Synth("mpeSynth", [\out, context.out_b, \freq, msg[2], \gate, 1], target:context.xg);
		});
		this.addCommand("noteOff", "i", { arg msg;
			var chan = msg[1];
			if (synths[chan] != nil) {
				synths[chan].set(\gate, 0);
			};
		});
		this.addCommand("freq", "if", { arg msg;
			var chan = msg[1];
			if (synths[chan] != nil) {
				synths[chan].set(\freq, msg[2]);
			};
		});
		this.addCommand("amp", "if", { arg msg;
			var chan = msg[1];
			if (synths[chan] != nil) {
				synths[chan].set(\amp, msg[2]);
			};
		});
	}
}

mpeTest.lua

engine.name = "MinimalMPE"

local notes = {0,0,0,0,0,0,0,0}

function init() 
end

local function getHz(note)
  return 13.75*2^(note/12)
end

local function note_on(channel, note, vel)
    notes[channel] = note
    engine.noteOn(channel, getHz(note))
end

local function note_off(channel, note, vel)
    engine.noteOff(channel)
end

local function getChannel(status)
    return bit32.band(15, status)
end

local function getEventType(status)
    return bit32.band(240, status)
end

local function midi_event(data)
  local channel = getChannel(data[1])
  local eventType = getEventType(data[1])
  if eventType == 144 then
    if data[3] == 0 then
      note_off(channel, data[2])
    else
      note_on(channel, data[2], data[3])
    end
  elseif eventType == 128 then
    note_off(channel, data[2])
  elseif eventType == 176 then
    --cc(channel, data1, data2)
  elseif eventType == 224 then
    local bend = 24.0 * ((data[3] * 127.0 + data[2] - 8192.0)/8192.0);
    engine.freq(channel, getHz(notes[channel] + bend))
  elseif eventType == 208 then
    engine.amp(channel, 0.3 * (data[2]/127.0))
  end
end

midi.add = function(dev)
  print('mpeTest: midi device added', dev.id, dev.name)
  dev.event = midi_event
end