Save audio file from app to iPad/iPhone library

I have been trying to figure out how to do this for most of the day, but I haven't been able to find much help. We have this multimedia app that 开发者_运维百科allows users to view pictures, videos, and music/ringtones about the particular subject. I know you can save images using UIImageWriteToSavedPhotosAlbum and you can save a video file using UISaveVideoAtPathToSavedPhotosAlbum. But I can't figure out how to allow the user to save an audio file. All the files are stored within the app, so its not like I'm trying to stream or download them from the internet. Does anyone have any pointers on how to do this?

The official SDK only allows you to retrieve information with MPMediaLibrary, no write access.