I have an APC Key 25 controller from AKAI and I bought the General MIDI Player so I could play the keyboard on it while studying music theory without having to fire up Ableton Live or another heavyweight software. So far I'm able to play it, but the only sounds coming out of it are piano sounds, no matter which instrument I choose on the General MIDI Player interface. Some of the buttons, other than the keyboard keys, will play notes with the currently selected instrument, but the keyboard will always play with a piano sound no matter what.
Changing the channel selection from the interface, I was able to find out that the keyboard seems to be sending MIDI messages to channel 2, since when channel 2 is selected only the keyboard keys will produce sounds, but I still only get piano. My MIDI knowledge is limited, but I'd assume that since interface of General MIDI Player suggests that it is getting messages from the hardware and then sending it to the selection of sound bank, this could be a bug. I wouldn't expect some keys of my controller to be fixed on a single instrument and couldn't find any options that might tweak this. I don't know if somehow sound bank selection could be baked in the MIDI messages my APC's keyboard is sending, but I still would expect General MIDI Player to be able to switch it to a different instrument, since other applications are able to.
Hope you can help me with this. Cheers!