Once somebody asked whether iTunes can work with Android and I said affirmatively NO, NO WAY, Apple would never allow that. But someone replied saying the contrary and he sounded so sure of himself. I did not follow up on that thread.
Anywhoo, I assume music on the iPhone, are synched to the PC, there is an image of the iPhone's music on the PC HD somewhere, unencrypted I hope. If that's the case then all you have to do is to find where they are stored on the HD and ask your Android App to use them.
Yeah, once you are "locked in" to the Apple ecosystem, they do make it difficult for you to defect. 🙁