Actually, that might provide a pretty decent return for the advertisers.
Some people don't like hearing music at night, but I can say I certainly do on many nights. I've basically given up my music collection for online radio (pandora.com), so no "night time" playlists. You might be on to something there.
I find that low-volume news/talk radio, like NPR or BBC makes me sleepier than music.
link: http://www.last.fm/listen/artist/Sigur%2520R%25C3%25B3s/simi...
It surely fills the 'nondiscernible lyrics' part though, and lispers will appreciate they have this album titled just ()
I just play a podcast or a playlist of sleep music on my iPhone in speaker mode (no headphones).
Guaranteed zero beat
I've nearly stopped listening to my entire music library, using this instead.
http://Sleep.FM .... sleep music and a web 2.0 alarm clock