so to set each track so its playable and readable correctly? i've had issues with BPM before and didnt even think twice that you could fix it. Mixed In Key detects the BPM and put's it in the BPM tag on the file for programs like itunes to read as they dont do BPM detection. If you import the song into traktor or serato, they do their own BPM detection when you analyze the song. Personally I'd rely on Traktor\Serato more for accurate BPM readings, but using Mixed In Key allows you to create itunes smart playlists based on BPM so you can import the playlist into other programs. opticon is pretty much spot on, as i said i manage my music library in itunes and i find it easy to have my song names titled as "KEY - BPM - SONG NAME" so at the click of the button i can have my playlist sorted by title and have a listing of all the songs sorted by key, then right beside the key i have a rough idea of what the bpm is keep in mind although the bpm analysers are pretty accurate these days, its still not 100% accurate, i just use them as a rough guide, its so if i have a track playing thats "5A - 128 - generic song title" playing, i can look at all the 4A, 5A, 5B, 6A tracks instantly and know their approx bpm very quickly