Implement All Sound Off CC message

[infojunkie]

I don't know if the original DX7 supported the All Sound Off CC message (type 120) but it would be useful to support it, especially that most Web MIDI implementations don't support the MidiOutput.clear() method which is supposed to clear the message queue on the sender side.

Supporting this message and/or All Notes Off (CC type 123) would help MIDI players achieve pause / stop functionality. Thanks!

[mmontag]

This is a great suggestion. I'll give it a try next time I work on this project.