Volume normalizers are notoriously ineffecient. I worked, professionally, in audio for 12 years dealing with live audio and studio recording as well as pre-and-post-production. Just listen to the iPod songs and then listen to them on a real stereo (properly outfitted of course) and you will probably notice much missing from the 'normalized' iPod versions that are present in your real CD versions. The data is there, the normalizers just tweak things poorly due to automation as opposed to hands-on action. Individual sliders are both easy to implement and would prove more effective.