I was wondering if this is a glitch in iTunes 11, or something else - has anyone else experienced such a problem? I purchased the 12-12-12 concert from iTunes and tried to play it off my Sonos system. I couldn't "see" it in the Sonos music library, and eventually realized that all the songs were m4p which is not supported by Sonos. In the past, all my purchases were m4a (or older purchases upgraded via iTunes Plus). I then noticed that in one of the drop down menus there was an option to convert files to AAC. So I figured I would give it a try - and voila, each song copied itself as an m4a file which hopefully is the same quality as the m4ps though I see that the file sizes are somewhat smaller. This strikes me as very odd.