MP3Gain analyzes and adjusts mp3 files so that they have the
same volume. 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.