I've always been rather fond of Fluxus. Beyond straight hypnagogia, it's my favourite music for relaxing and actually listening to. Night time, dim lights, no distractions, not doing anything else. Just listening.
My favourite Fluxus artist (of those I know, i'm no expert) is probably Henning Christiansen. The only downside is that his stuff goes for crazy money, so it's pretty difficult to get hold of.
Kye (a great label for this kind of music) reissued an excerpt of Christiansen's original 'Kreuzmusik' cassette last year. You can hear a snippet here: http://www.youtube.com/watch?v=SrzmpPHoc_w
You want the original full length cassette? There's one going for the very reasonable £1,539.70 on discogs.
Here's another extract from his Symphony Natura album: http://www.youtube.com/watch?v=ZXG4we0zanI
Let's celebrate all things Fluxus!
(If anyone dares mention Yoko Ono in this thread i'm going to come round your house and cut your face)