Sends a noteon and a noteoff MIDI message both with the same channel, number and velocity.
ichn -- MIDI channel number (1-16)
inum -- note number (0-127)
ivel -- velocity (0-127)
idur -- how long, in seconds, this note should last.
noteondur (i-rate note on with duration) sends a noteon and a noteoff MIDI message both with the same channel, number and velocity. Noteoff message is sent after idur seconds are elapsed by the time noteondur was active.
noteondur differs from noteondur2 in that noteondur truncates note duration when current instrument is deactivated by score or by real-time playing, while noteondur2 will extend performance time of current instrument until idur seconds have elapsed. In real-time playing, it is suggested to use noteondur also for undefined durations, giving a large idur value.
Any number of noteondur opcodes can appear in the same Csound instrument, allowing chords to be played by a single instrument.