If there is a match it uses the 256 AAC file you would have get if you buy the song in iTunes. If it is not matches, it uploads your original file. It was a g

If there is a match it uses the 256 AAC file you would have get if you buy the song in iTunes. If it is not matches, it uploads your original file. It was a good way to migrate from 128kbps MP3 to high quality 256 AAC