Adding of 2 more states for the Metronome:
0 - off
1 - Rec
2 - Play&Rec
Currently the Metronome can just be turned on or off.
Sometimes it is helpful to be able to hear the Metronome even if one is not
recording, eg. practising a synthline before recording, or keeping track of an
intricate rhythm during playback. Or just for figuring out the tempo of a loop.
Put the tracker on record to hear the metronome.