This class adds state and controls to the basic PianoKeyboardMorph so that notes of reliable duration can be keyed into a score without the need for a real keyboard.

To try this out, execute...

| n score | n _ 3.
score _ (MIDIScore new tracks: ((1 to: n) collect: [:i | Array new]);
trackInfo: ((1 to: n) collect: [:i | 'Instrument' , i printString]);
tempoMap: nil; ticksPerQuarterNote: 96).
ScorePlayerMorph openOn: score title: 'empty score'

Then open a pianoRoll and, from that, open a keyboard. The rule is that the keyboard will append after the current selection. If the current selection is muted or nil, then input will go to the end of the first non-muted track.

	initialization
	addRecordingControls initialize pianoRoll:

	note controls
	articulation:onOff: backspaceNote buildChord: deleteNotes durMod:onOff: duration:onOff: emitRest fullDuration noteDuration velocity

	events	top
	mouseDownPitch:event:noteMorph:
	mouseUpPitch:event:noteMorph:
	soundForEvent:inTrack:

	initialization	top
	addRecordingControls Add chord, rest and delete buttons
	initialize
	pianoRoll:

	note controls	top
	articulation:onOff: artic = eg, #legato, #normal, #staccato.
	backspaceNote
	buildChord:
	deleteNotes
	durMod:onOff: durMod = eg, #dotted, #normal, #triplets, #quints
	duration:onOff: denom = eg, 1, 2, 4, 8, 16
	emitRest All this selection logic should be shared with mouseDown...
	fullDuration
	noteDuration
	velocity