When you say, 'connecting' do you mean via AudioBus (which should work—I have tested this and it works—recording to a track in GB as iReal Pro is playing. Initially there were a few problems with running AudioBus in iOS 8 but they are gradually being fixed).

Or do you mean, GB does not list in the Open in... menu? I have used the app AudioShare (which shows in the Open in menu) then to General Pasteboard, and paste into GB (use wav format).
There are other options. I am assuming you mean GB on your iOS device?

Or do you mean on your Mac? in which case you can email the midi file or AAC, or use file sharing with iTunes to find the audio file you Saved, and save (drag) to your Desktop, then import to GB (wav is better quality).


I probably need more information to help you further.