I've noticed in some of the Music reply sections about VA uploads having differing degrees of sound levels and how annoying that can be. When I was really into music collecting, one the tools I used was MP3 Gain from Sourceforge.net. It would normalize a batch of files to what ever volume levels you desire. It was also a good tool to help with clipping. There may be something better out there now. But it worked really well for me back in the day. If you want to give it a try here it is.
http://mp3gain.sourceforge.net/
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