A Boolean value that indicates whether or not the sequencer's player is playing.
- iOS 9.0+
- macOS 10.11+
- Mac Catalyst 13.0+
- tvOS 9.0+
true if the sequencer's player has been started and not stopped. It may have played past the end of the events in the sequence, but it is still considered to be playing (with its time value increasing) until it is explicitly stopped.