Add a new control mode for changing transposition

Enter transpose mode: Press keys for "Low B" and draw air for ~1 sec. Haxo will play two notes to indicate mode has started.
Jump directly to a transposition: Press the keys you want a written "High C" to sound like (in concert pitch), and blow air until you hear two beeps in confirmation (concert "High C" and transposed "High C"). e.g. to get a tenor saxophone, play "Mid Bb" (which is 14 semitones below high C, which is how far below concert a tenor sax sounds). See table below
Further adjust the transposition: press R1 to transpose up a half-step, press R3 to transpose down a half-step (same keys as for changing instrument sounds. You will hear two beeps in confirmation (concert "High C" and transposed "High C")
Exit transpose mode: Press three left palm-keys. You will hear a single beep in confirmation.

Note to play to jump directly to transpositions of different saxophones:	instrument	play
soprano	High Bb
alto	Mid Eb
tenor	Mid Bb
bari	Low Eb

@jcard0na I'm pretty happy with how the implementation turned out, but I'm happy to incorporate any feedback you may have

cardonabits / haxo-rs