I love Sigur Rós, but while the tempo is calm, the songs often get intensely emotional (if you watch them live, you'd think the drums guy does heavy metal in his other life.) Their music brings me peace, but it keeps me awake.

It surely fills the 'nondiscernible lyrics' part though, and lispers will appreciate they have this album titled just ()

http://tinyurl.com/5lfpc2