I implement one polyphonic channel of a 16-channel MIDI synthesizer. Many MIDI commands effect all the notes played on a particular channel, so I record the state for a single channel, including a list of notes currently playing.

This initial implementation is extremely spartan, having just enough functionality to play notes. Things that are not implemented include:

1. program changes
2. sustain pedal
3. aftertouch (either kind)
4. most controllers
5. portamento
6. mono-mode

	initialization
	initialize

	midi dispatching
	channelPressure: control:value: doChannelCmd:byte1:byte2: key:pressure: keyDown:vel: keyUp:vel: pitchBend: programChange:

	other
	adjustPitch: convertVelocity: newVolume:

	accessing	top
	instrument
	instrument:
	masterVolume
	masterVolume: Set the master volume the the given value (0.0 to 1.0).
	muted
	muted:
	pan
	pan: Set the left-right pan to the given value (0.0 to 1.0).

	initialization	top
	initialize

	midi dispatching	top
	channelPressure: Handle a channel pressure (channel aftertouch) change.
	control:value: Handle a continuous controller change.
	doChannelCmd:byte1:byte2: Dispatch a channel command with the given arguments.
	key:pressure: Handle a key pressure (polyphonic aftertouch) change. Rarely implemented.
	keyDown:vel: Handle a key down event with non-zero velocity.
	keyUp:vel: Handle a key up event.
	pitchBend: Handle a pitch-bend change.
	programChange: Handle a program (instrument) change.

	other	top
	adjustPitch: Handle a pitch-bend change.
	convertVelocity: Map a value in the range 0..127 to a volume in the range 0.0..1.0.
	newVolume: Set the channel volume to the level given by the given number in the range 0..127.