Is there a way to load m4a in iOS?

I am making a music game for iOS and I want to load the music from iTunes and analyse it. I have a plug-in to get the music file but unity can't decode it if it's not mp3. But as far as i know, many music in itunes is usually m4a. Therefore I really want a way to load m4a. I tried NAudio but it seems it only has MediaFountain which called Windows 7 library.

PS Calling iTunes to play music is NOT what I am going to do. I want to load its audio signal so that i can analyse it