Please check the app "Highnote". It allows you to select a local track in your iPod library. It will then somehow recognize this track and you will be able to "send" that track to some one else.
Instead of really sending any audio though they merely send some iTunes reference id/link information and will allow you to pre-listen to 30s of that track and/or buy it from iTunes.
The task is to create a demo app (no need for any fancy ui - this is just meant as a tech demo) that will allow me to select a track and will then allow me to pre-listen to that track on iTunes (wihtin the app) and optionally buy it.
If the functionality does not seem clear to you but you feel that you are an experienced iOS coder then please take a moment to install that free app from the AppStore to check it out yourself.