A reader for Standard 1.0 format MIDI files.
MIDI File Types:
type 0 -- one multi-channel track
type 1 -- one or more simultaneous tracks
type 2 -- a number on independent single-track patterns

Instance variables:
stream source of MIDI data
fileType MIDI file type
trackCount number of tracks in file
ticksPerQuarter number of ticks per quarter note for all tracks in this file
tracks collects track data for non-empty tracks
strings collects all strings in the MIDI file
tempoMap nil or a MIDITrack consisting only of tempo change events
trackStream stream on buffer containing track chunk
track track being read
activeEvents notes that have been turned on but not off

	private
	guessMissingInstrumentNames next16BitWord next32BitWord: readChunkSize readChunkType readVarLengthIntFrom: report: riffSkipToMidiChunk scanForMIDIHeader splitIntoTracks

	track reading
	endAllNotesAt: endNote:chan:at: isTempoTrack: metaEventAt: readTrackContents: readTrackEvents startNote:vel:chan:at: trackContainsNotes:

	chunk reading	top
	asScore
	readHeaderChunk
	readMIDIFrom: Read one or more MIDI tracks from the given binary stream.
	readTrackChunk

	private	top
	guessMissingInstrumentNames Attempt to guess missing instrument names from the first program change in that track.
	next16BitWord Read a 16-bit positive integer from the input stream, most significant byte first.
	next32BitWord: Read a 32-bit positive integer from the input stream.
	readChunkSize Read a 32-bit positive integer from the next 4 bytes, most significant byte first.
	readChunkType Read a chunk ID string from the next 4 bytes.
	readVarLengthIntFrom: Read a one to four byte positive integer from the given stream, most significant byte first. Use only the lowest seven bits of each byte. The highest bit of a byte is set for all bytes except the last.
	report:
	riffSkipToMidiChunk This file is a RIFF file which may (or may not) contain a MIDI chunk. Thanks to Andreas Raab for this code.
	scanForMIDIHeader Scan the first part of this file in search of the MIDI header string 'MThd'. Report an error if it is not found. Otherwise, leave the input stream positioned to the first byte after this string.
	splitIntoTracks Split a type zero MIDI file into separate tracks by channel number.

	track reading	top
	endAllNotesAt: End of score; end any notes still sounding.
	endNote:chan:at:
	isTempoTrack: Return true if the given event list is non-empty and contains only tempo change events.
	metaEventAt: Read a meta event. Event types appear roughly in order of expected frequency.
	readTrackContents:
	readTrackEvents Read the events of the current track.
	startNote:vel:chan:at: Record the beginning of a note.
	trackContainsNotes: Answer true if the given track contains at least one note event.

	as yet unclassified	top
	playFileNamed:
	playStream:
	playURLNamed:
	scoreFromFileNamed:
	scoreFromStream:
	scoreFromURL:
	standardMIDIInstrumentNames Answer an array of Standard MIDI instrument names.