While music catalogs have endless supplies of cues available to music supervisors, a show looking to stand out will look for vocals (presumably during montages and not under dialogue). From the Boston Herald:
“My mailbox is stuffed with 400-plus submissions a week, but I still go looking for songs, too,” said Alex Patsavas, music supervisor for both “The O.C.” and “Grey’s Anatomy.” “While there’s plenty of instrumental material around to fit almost any scene, it’s become a powerful creative choice to have vocals that somehow comment on the story line.”
It’s interesting that a music supervisor *only* gets 400 email submissions a week. As for the submitters’ chances, it probably matters who is doing the emailing. Still, 1 in 400 is not a bad shot, more unknown acts ought to try.
The story goes to talk about unknown, some even unsigned acts that have gotten onto shows – my favorite is probably The 88 (though I’ve never seen How I Met Your Mother, the show that featured them).