Hi Mog and Bewellalso,
What do you think about the following CD:
http://www.islandmusicstore.com/SonicaidMusic.htm
There is also a brain entrainment concentration cd. I'm not sure which CD would be better. Ultimately you want something that helps you focus on the echoes but helps you relax and meditate.
So which CD's do you both recommend? If you could both pick one or two CDs that are the most effective, which would it be?