iTunes 11 is completely redesigned with interface just like an iOS App. iTunes 11 brings it more fun to explore and enjoy your music, movies, and TV shows.  .FLAC file is losslessly audio format which provides marvelous audio quality but much smaller file size. It’s pity however, iTunes 11 does not natively support play FLAC files.

Visit detailed guide on how to add FLAC to iTunes 11 to play FLAC files in iTunes 11