I don't have suggestions for this type of music, but wanted to add a comment just to think about: you may not want music during labor after all. I thought I'd want music, and put some together, and when my DH asked me what I wanted to hear I said "absolutely nothing!" I was in laborland, and music would have (for me) broken that.
I'm sure for other mamas music may help, not hinder that.
Anyway I hope my comment was helpful and not unwanted. I just wanted to share that since my expectation of birth was a little different, and it turned out that I needed to concentrate more than I needed to relax (candles, music, etc.).
I always thought Peter Gabriel's Passion would be perfect to labor to. It's very lush, middle eastern sort of music, mostly instrumental. But I ended up wanting upbeat (dancing) music in early labor, and in late labor I wanted it QUIET.
During most of my labor I really wasn't aware of sounds around me, but I do remember DH putting in a Ladysmith Black Mambazo CD which we had brought with us. It's a CD that has pleasant, relaxing associations for us.