The MKPerformer Class

• An abstract class that dispatches MKNotes in a time-ordered fashion. MKPerformers are active; they are MKNote dispatchers.

• Subclass implements perform, invoked periodically by its MKConductor, as determined by the instance var nextPerform, reset within perform to specify when next MKNote is to occur.

• Table 3-4. MKPerformer subclasses provided by the MusicKit

  Class	Means of performance
  MKPartPerformer	performs MKNotes from a MKPart.
  MKFilePerformer	(abstract) performs MKNotes from a file.
  MKScorefilePerformer	performs MKNotes from a scorefile.
  MKScorePerformer	manages a set of MKPartPerformers
  MKMidi	(abstract) performs MKNotes it receives via MIDI

• MKPerformers send MKNotes via their “outputs”, small objects called MKNoteSenders. A MKPerformer sends a MKNote to one of its MKNoteSenders: [aNoteSender sendNote: aNote];

  Table 3-5. MKNoteSenders provided by MKPerformer subclasses.

  Class	Number of MKNoteSenders
  MKPartPerformer	1
  MKScorePerformer	1 per MKPart in the MKScore
  MKScorefilePerformer	1 per MKPart in the scorefile
  MKMidi	1 per MIDI channel + 1 extra

• MKPerformers may be paused, resumed, delayed, and created dynamically. Similar to Pla “voices” or Common Music “parts”.