The MKInstrument Class

• An abstract class that realizes MKNotes in a manner defined by the subclass. MKInstruments are passive, they respond to MKNotes sent to them by the user interface or a MKPerformer.

• The subclass defines its means of realization by implementing realizeNote:fromNoteReceiver:.

• Table 3-1. MKInstrument subclasses provided by the MusicKit

  Class	Means of realization
  MKPartRecorder	adds MKNotes to a MKPart.
  MKSynthInstrument	realizes MKNotes on DSP.
  MKFileWriter	(abstract) writes MKNotes to a file.
  MKScorefileWriter	writes MKNotes to a scorefile.

• Table 3-2. Pseudo-Instrument classes provided by MusicKit

  Class	Means of realization
  MKMidi	sends MKNotes to MIDI via serial port
  MKScoreRecorder	manages set of MKPartRecorders

• MKNoteFilter is a special (abstract) subclass of Instrument that processes MKNotes it will be described later.

• MKInstruments receive MKNotes via their “inputs”, which are small objects called MKNoteReceivers. You can send MKNotes directly to a MKNoteReceiver or use a MKPerformer to dispatch the MKNotes (e.g. when playing a MKScore).

  Table 3-3. MKNoteReceivers provided by MKInstrument subclasses

  Class	Number of MKNoteReceivers
  MKSynthInstrument	1
  MKPartRecorder	1
  MKScoreRecorder	1 per Part in the Score
  MKScorefileWriter	1 per MKPart in the scorefile
  MKMidi	1 per MIDI channel + 1 extra

• You can tell an MKInstrument to realize a MKNote by sending receiveNote: to one of its MKNoteReceivers. You can obtain the MKNoteReceiver in various ways. To get its first MKNoteReceiver, send noteReceiver to the MKInstrument.

• When sending MKNotes directly to an MKInstrument's MKNoteReceiver, you must update time. Afterwards (if using the DSP) you must make sure that the DSP command buffers are properly emptied. Example:

  [MKConductor lockPerformance]; [[anInstrument noteReceiver] receiveNote: aNote]; [MKConductor unlockPerformance];