I just dragged an m4p audio file from my itunes into FCP and all though it shows up in the bin, it will not playback? It's a song purchased off itunes.... protected?
Not only that, but FCP doesn't play well with the "compressed files". You need to burn the song to a CD which will convert it to AIFF. You can then bring it back into FCP. Just be aware that you will still need clearances for anything you are going to "distribute" i.e. anything other than personal use and not shown publicly...which of course includes YOUTUBE.
Oddly enough, Apple provides you with software to take the Apple DRM off of protected music files and convert it to aiff...iMovie. Easier than outputting to CD.
Fortunately DRM seems to be dying (albeit slowly) at the iTunes store.