Here’s the jist of it: they had a bunch of music experts listen to thousands and thousands of songs, and categorize something like 80 technical qualities about the sounds that only music theorists really understand. Then, you tell the system what artists or songs you like, and the system looks for songs that are musically similar based on those categorizations.

I set up a few channels a couple of weeks ago. When songs I don’t like come up, I give it a thumbs down. When a particularly good one comes up, I give it a thumbs up. The system keeps track of this, learns my preferences, and makes better and better suggestions.

After a couple of weeks, it is just about perfect. It plays song after song after song, and I like them all. And it’s playing 75% songs I’ve never heard before.

Now, here’s the amazing part. I started with a list of mostly hard rock artists I like: Jane’s Addiction, Foo Fighters, etc. I figured I would get back hard rock only. But, it comes back with a lot of folksy alt-rock and some pop, and I even got one tune that I would classify as “funk.” The common thread: all of it is really good. It’s algorithm is somehow good enough to filter out all of the pop music that I don’t like.

There’s a menu item that you can click to tell you why it’s playing a certain song. It’s basically a way to ask the artificial intelligence which characteristics of the song matched the things it thinks you like. Here are some examples that I got back:

Based on what you’ve told us so far, we’re playing this track because it features mellow rock instrumentation, a subtle use of vocal harmony, mild rhythmic syncopation, acoustic sonority and major key tonality.

Of course, I have no idea what this means. I probably know someone or other who could explain “mild rhythmic syncopation” or “acoustic sonority,” but I won’t remember to ask. The one thing that I need to tell it is that female vocalists are okay. I don’t get any sings with female singers at all.

Here’s a five-song playlist of songs I never heard before this morning. I know that no one will actually follow up and try to listen to any of these, because I see such things, and I don’t follow up and try to listen.

• Jets to Brazil - You’re Having the Time of My Life
• So Beautiful - Dashboard Confessional
• Placebo - Pure Morning
• Diamond Nights - Dirty Thief

Happy listening.