MP3Gain does not just do peak normalization, as many normalizers do. Instead, it does some statistical analysis to determine how loud the file actually sounds to the human ear.
Also, the changes MP3Gain makes are completely lossless. There is no quality lost in the change because the program adjusts the mp3 file directly, without decoding and re-encoding.
The author of MP3Doctor recently renamed his "SuperMp3Normalizer" program to "Mp3Gain PRO". I did not write this new program, so please do not email me any support questions about it.
If you're interested, here are the main technical differences between "Mp3Gain PRO" and my, uh, "classic"(?) MP3Gain:
"Mp3Gain PRO" does volume normalization inside the mp3, not just between separate mp3s. So if you feel a song is too quiet at the beginning (or middle, or end), then it can boost the volume just for that part. Pretty cool, if that's what you need.
The changes "Mp3Gain PRO" makes are not undo-able. In order to make its fine-tuned adjustments, it must re-encode the mp3 file.
