Quality and Volume loss when when exporting mixdown from Garageband to iTunes SOLVED!!!
This is a simple work-around, but after experiencing the same frustration of others and reading a multitude of discussions with no real solution, this is what I have found: "save file to disc". This saves the song to a location you designate on your Mac as a .AIF file which is basically like a .wav, with NO added compression and NO volume "normlizing". In other words, it pretty much sounds like what you hear when you listen to your project in garageband! Granted, it does take up considerable memory- in my case a 5.5 min song was nearly 90Mb. After the export, open a "Finder" window, locate the file, and open it; it will automatically open in iTunes. Now in iTunes at full quality, you can right-click the song and "make mp3 version". Once created, I admit the mp3 did have a few places where the bass "peaked-out", and it took several reps of going back to my gb project to adjust the volumes down at just the problem areas on those tracks where the bass was peaking, but after a handful of times I had it! And no arbitrary volume loss imposed by gb! I'm telling you, it's the closest you can get your export to the original project!
iPhone 5, iOS 6.1.3, GarageBand App No Low Frequency