iGain is a front-end for AACGain to enable it to work better with iTunes.
DRM'ed files purchased from the iTunes music store are not supported. You may convert these to .m4a format by burning them to a CD-ROM and importing them back into iTunes.
iGain/AACGain does not work with Soundcheck. Soundcheck should be turned off in both iTunes and your iPod.
iGain/AACGain does not modify the iTunNorm tag that is used to display volume in iTunes. You will not see any change in the iTunes displayed volume after making adjustments. You will hear the changes on playback.
iGain requires iTunes version 4.6 or later. If iTunes is not found on your PC, iGain will not start.
iGain/AACGain supports files in the mp4/Quicktime file format. These files usually have a file extension of .mp4 or .m4a. Raw AAC files, or files encoded with HE-AAC/SBR are not supported.