As the movie-based-on-the-book High Fidelity would tell you, there are rules to creating the perfect mix of music. The best bridge between jazz and country-western is Lyle Lovett. Johnny Cash goes surprisingly well with grunge. And you never, ever mix ABBA with the Sex Pistols.

You’ll soon hear if the newly available Genius music recommendation service makes or breaks these rules when you get your first earful after downloading iTunes 8. With a touch of a button on your iPod’s on-screen controls, Genius finds songs that “go great” with your choice of music, based on songs from your library.

During the Let’s Rock event today, Steve Jobs did not explain how the playlists would be collated. (Beats per minute? Year the song was released? Songs sung by musicians who have OD-ed?). But Apple’s PR explained these new playlists based on the music preferences of all of iTunes other users.

Including you.

According to Apple’s PR, “Information about your music library is anonymously sent to the iTunes Store, where it is combined with the anonymously-gathered knowledge from millions of other iTunes users and processed through Apple-developed algorithms.”

Turn Genius on, and it will gather the details of the songs you’ve purchased and upload them to the mother ship. Based on the history of other users, if you purchase Avril Lavigne, Apple can easily recommend Pink. Paranoid people, rest easy: Apple won’t be able to hold your purchase of Fergie’s “London Bridge” against you
 
These playlists can be created, modified, and saved with ease on both iTunes and your iPod. Genius also recommends songs not currently in your library, so you can buy them (for the usual $.99, natch) and perfect your new playlist.

Music recommendation services are not unique to Apple. Pandora radio has carved a niche for itself with recommendations. And online music store Amie Street blends recommendations with social networking. But these services don’t integrate recommendations with the iPod the way Apple does.

Playlists made just for you in one touch. This simple yet powerful feature is yet another reason why Apple Inc. continues to lead the world of digital music and others only follow.

For more information, see the iPod touch guided tour and Apple's Genius page.