Hey, I really should do a public service here and provide the same Audio Editor I use so that you can edit the volume of the MP3 before burning it.
Here's what I use for audio editing: Goldwave
http://www.goldwave.com/release.phpAlso, a lot of people use Audacity, (but I like Goldwave better)
http://audacity.sourceforge.net/EDIT: Only Audacity has a Mac version. So, if you're David Shand, get an Audacity for mac os. :PBefore burning your themes to a disc, turn them down by using the "change volume" setting after loading the MP3 into the program. Not sure exactly how much quiter you'll have to make them. I'll experement with it and give an exact percent that's good.
Then "Save As" to re-export your song. A good bitrate and frequency to save as is 44100 and at least 128kb. Up to 320kb is optimal.
As I said, i'll see exactly what a good volume is, but at this point, i'd guess that turning it down from 100% to about 50% should be good. Maybe 60%. I'll look into it.