Polyphonic instrument in SuperCollider

polyphonic_prototype.sc

// ISC License
//
// Copyright (c) 2022 Jakob Dübel
//
// Permission to use, copy, modify, and/or distribute this software for any
// purpose with or without fee is hereby granted, provided that the above
// copyright notice and this permission notice appear in all copies.
//
// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
// REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
// AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
// INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
// LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
// OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
// PERFORMANCE OF THIS SOFTWARE.

// Initialize MIDI
(
MIDIClient.init;
MIDIIn.connectAll(verbose: true);
MIDIFunc.trace(bool: true);
)

// Global variables for housekeeping
(
~master_group = Group.new(Server.default);
~mep = MIDIIn.findPort(deviceName: "UA-25", portName: "UA-25 MIDI 1");
~srcID = ~mep.asMIDIInPortUID;

// The state of the keybed. Each key can be pressed or not.
~keys = Array.fill(128, { False });

// The state of the sustain pedal. Released is 0, pressed is 1. Some hardware allows for values in between.
~sustain = 0.0;

// One group for each key to store Synths.
~groups = Array.fill(128, { Group.new(~master_group, \addToTail) });
)

// Functions to handle MIDI NoteOn, NoteOff and the sustain pedal, which is Control Change 64
(
~handleNoteOn = MIDIFunc.noteOn({
	arg ...args;
	var velocity, amp, note, freq;
	velocity = args[0];
	note = args[1];
  
	~keys[note] = True; // key pressed

	// Start a synth voice and store its handle in the appropriate group.
	Synth(defName: \default,
		args: [
			\freq: note.midicps,
			\amp: velocity.linlin(0, 127, 0.0, 0.2)
		],
		target: ~groups.at(note)
	);
});


~handleNoteOff = MIDIFunc.noteOff({
	arg ...args;
	var note, freq;
	note = args[1];
  
	~keys[note] = False; // Key released

  	// If the sustain pedal is up, end the Synth voice
	if (~sustain < 0.5, {
		~groups[note].set(\gate, 0);
	}, {
		// else nothing
	});
});


~handleSustainPedal = MIDIFunc.cc({
	arg ...args;
	var value;
	value = args[0].linlin(0, 127, 0.0, 1.0);

	~sustain = value; // Update the stored state used in above functions
  
	if (value < 0.5, {
		// If the pedal is released, end all synth voices, whose key is not pressed
		~keys.do({
			arg value, note;
			if (~keys[note] == False, {				
				~groups[note].set(\gate, 0); // Release the ringing notes
			}, {
				// else nothing
			})
		});
	}, {
		// If the pedal is pressed: do nothing.
	});
}, ccNum: 64, chan: 0, srcID: ~srcID);
)

This code allows to play the \default Synth in SuperCollider polyphonically with a MIDI keyboard. The number of running synths is not limited, so XRUNs are possible.