I know how to do it between Android devices, but harder to do with Apple closed nature. On Android, I can run CheapCast on one Android device, and use a different Android to cast Play Music to it, but there are other ways as well. DroidMote is one app that let one Android control another.
On iOS, instead of Google Music, you could use Plex. It involved some work. Set up the Plex Media Server on your PC and add music to the library. Buy Plex on Android and iOS, this will be $10 total. On iOS set Plex to act as Google TV, then use the Android Plex to cast the music to the iOS Plex, but in actuality it will steam the music from your Plex server.
Or maybe you can use TeamViewer from Android to remote desktop to iOS's TeamViewer QuickSupport. Probably not practical.
I have no experience with jailbroken iOS so maybe it have lots more options.