Why does my iTunes music folder take up more space than my iTunes library??

hi,

my first impression is that you have songs in your iTunes music folder that, for some reasons, are no longer refered within your iTunes library. for exemple, if at some point you have deleted songs from your iTunes library without answering "move to trash" but "keep files", you may end up having song files that will no longer appear in your iTunes list.

AAC stand for Advanced Audio Coding. The resulting file created using this codec will be called M4A; so it is perfect normal that your AAC encoded files appears in the M4A format. But it is very odd that you see a big difference in between the Finder file size of the M4A compared to the iTunes results. Could you take an exemple and post the numeric result of the file size to quantify what you mean by "huge" difference?

Using AAC instead of MP3 is, from my point of view, the best choice. But you should avoid converting your MP3 to AAC that will reduce your song quality. The best way to get all the quality from the AAC compression is to import in AAC from the original. Change your import setting to AAC, insert your CD and click import; iTunes will automatically detect your MP3 and prompt you to replace them with the AAC version.

Are you managing the files yourself or is iTunes managing them for you? Since iTunes copies all files into the library, you might have several files twice. That could be if you had an already sorted library of music in the music folder and dragged everything in iTunes, which would then put them down a second time.