Add: incoming MIDI notes now select new home note. This makes it
possible to (deterministically) change the key of the instrument,
if you have a MIDI keyboard. This also allows it to act sort of
like one of the Yamaha BC-3 breath controllers. I could also
have a mode where all sounding notes on the BlowChucks are
controlled by an external keybaord, and then it would act just
like a breath controller.

Also, flash the LED on incoming and outgoing note on/off
messages, as a troubleshooting aid.