I am sure you have already thought of this, but you say your i-pod only lasts 4 hrs, and then after that you leave them on to just block out the noise. Why not buy 2-3 more i-pods, stock them all with the same songs, and when one battery goes under, you put the other one on, and have a little case for them all, that way your i-pod(s) will never run out of battery, and you can always listen to them while playing. I figure this might be productive for you, and help you listen to massage music when you feel the need to.