if you can only hear "piano" it sounds like a midi-setting problem:
Which keyboard do you use, company and model ??
On which MIDI-Channels is your keyboard transmitting ???
You should have set "split" mode to "on" and ensure that right part is transmitting on channel 1 and left part on channel 2 ( if you use "accordion1"-setup in Audya .)
Normally midi-in1 of Audya should work, if not, try midi-in2.
Greetings from East-Frisia ( Northern-Germany )