I'm the developer...just trying to clarify a a few things. When used across your entire collection, mp3gain will reduce the levels of MP3s that are loud (most commercial, rock/pop) and bring up those that are quiet by modifying the gain value in each frame of the MP3 file. This is a lossless technique that will travel with the MP3 file wherever you use it rather than iTunes' method which only works from within iTunes. If you use a portable MP3 player or a networked player like the AudioTron (as I do), then this helps reduce your trips to the volume control. As for the question of whether this affects audio CDs burned from iTunes, the answer is yes...if mp3gain reduced the level of the MP3, then the resultant CD's level will be lower than the original.