A user recently contacted with a problem, in which his iCON iKeyboard device was not working properly. The keys would not trigger notes to play in GM Player, but presses on the devices buttons would trigger notes. He sent the screenshot below which gave a clue to the problem - the device presented itself as two different devices, one for the keys, the other for the controller buttons.
This presented a problem for GM Player, as it is currently written to distinguish MIDI devices by their names, and so having two identical ones caused it to get "confused."
The solution to the problem was to go to the Mac's Audio MIDI Setup app, and to create a new MIDI device with 2 ports, connecting it to the original iCON device, and naming each port something unique. See image below.
This allowed GM Player to differentiate between the two inputs correctly.
Hopefully this helps someone else!