Any Ipad music Apps which allows you to play your midi instrument as background audio

[urazyjazzy]

the title explains itself. are there any apps like garageband or synth apps such as ipiano or music studio etc... which would let me play the instrument via camera connection kit and read a pdf document at the same time. For example lets say I am playing the piano within the application garageband and I wanna read music charts that I have in my ipad via pdf reader but whenever I put the garageband app in to background it stops functioning. so you can not make garageband work with any other app...
Anybody knows any app conducive for my goal...???