Don't have any particular songs in mind but songs without words in them are good because when you hear words in a song or some is talking to you etc it makes you use the language part of your brain (sorry forget what its called) and stops you from using your primitive brain.
Tan - my doula and her back-up have both given me the following advice in line with Antheia's. Birthing is primitive - and listening to songs with words or even music that is very familiar to you makes you change from primitive to cognitive - therefore more focus on words and tunes and less on birthing etc ..... ???? Sounds right to me, I have revamped my labour music now too. Also recommended is music that has a beat slower than your heartbeat - do you have any movie soundtracks or know anyone that does??? They are good for a flick and some tracks etc. Also, check with your doula that she doesn't have some loaded ready to go in an Ipod dock in birthing suite too ....