I did have a soundtrack once, but it wasn't by my doing. It just happened.

But I have read, tha all you have to do is to think about your favorite piece, and it will start playing. I don't really think you need to know the song well enough. Just the same way as you are able to play it in your head. I found, that in dreams I remember more things than in waking like. So even if you think you don't know something well, you may know it quite well.

And I have also heard, that music can be so much more beautifull than in WL. I already have a melody ready to request from astral jukebox.