My favorite hard-to-find but very cool suggestion is Mouth Music, but it's out of print. I recently tried to get a copy of it on CD as a gift and was unable to. I ordered what I thought was a CD copy from an international distributor, and got a cassette instead. I just now placed an order for a Used copy through Amazon and I'm hoping this one pans out.

The album is essentially a collection of old Scottish folk tunes, known as "puirt-a-beul", sung in the original Gaelic (with the translations written on the lyric sheet). However, they have been set to interesting modern rhythms, productions, and arrangements. This is mixed with some pure-instrumental stuff as well as some pure a-capella singing of the folk tunes as they were originally written. It's a very atmospheric album with great textures. Standout tracks are "Martin, Martin" and "Chi Mi Na Morbheanna".