Thirty-second song samples from iTunes are a thing of the past. Anyone looking to expand their music collection or discover new artists can turn to Pandora—a free online, commercial-free radio that plays music based solely on your musical tastes.

Pandora takes information about the band you type in: their style, roots, and influences. It then creates a radio station that plays artists similar to those you entered.

If you’re looking for something less specific, Pandora lets you create radio stations by genre as well. You can select from one of 18 genres, which are composed of four to 19 subgenres, offering a vast 143 different choices.

The layout is easy to use, and it gives you more control than any online radio station I’ve encountered.

If you don’t like a song, you can click a “thumbs down” button. Pandora immediately stops that song, making note to never play it for you again, and looks for something different. If you “thumbs down” that same artist five times, it will never play the artist again. Clicking the “thumbs up” fine-tunes the search to closely match that exact song.

In addition, Pandora gives you volume control, a play/pause button, and a “skip track” button. “Skip track” goes to the next song, but can only be used six times per hour.

Another cool feature is the popups that give a breakdown on how Pandora selects the songs.

The popup tells you what defines your artist: minor key tonality, Latin beats, rhythm guitars, and why it chose to play songs from similar bands.

Deciding to test the accuracy of its “music matching,” I searched for the Foo Fighters.

Under a “radio stations” tab appeared a station called “Foo Fighters.” It began to play a song of theirs, and explained in a pop-up “We’re playing this track because it features hard rock roots, punk influences, mild rhythmic syncopation, extensive vamping, and intricate melodic phrasing.”

It went on to explain that it would use that information to choose songs it deems similar to the Foo Fighters.

It first played a popular Foo Fighters song and then played “Slither” by Velvet Revolver.

I didn’t like the song so I gave it a “thumbs down.” Pandora skipped to the next song and wound up playing artists Live, Stone Temple Pilots, Red Hot Chili Peppers and Pearl Jam.

I liked these bands, and found them very similar to Foo Fighters.

During my eight-song test it also played Foo Fighters songs four times. Pandora isn’t restricted to the most popular artists.

If Pandora starts playing too many songs from the same artist, or if you just become sick of a particular artist, you can ban an artist from playing on a station for one month.

Fans of the obscure won’t be disappointed. Even if no one you know has heard of your favorite band, there’s still a good chance Pandora has. I tried searching for the experimental Dredg and the centuries-old Beethoven. Both searches yielded results.

Pandora puts the songs and artists it plays for you on a list. You can click on the name of the artist for their information and for a list of artists similar to them.

But Pandora is a radio, not a playlist. You cannot go back and listen to a song again unless, by chance, Pandora chooses to play that song again.

You don’t get control (with the exception of six skips per hour) over the songs it plays. You only get control over the type of music it plays.

Thus Pandora is a good option if you’re looking for something new or just feel like listening to “techno.”

Visiting www.pandora.com and creating a free account allows you to save your radio stations and listen to them on your iPods and iPhones via the application pandora just released.

To make things easier, Pandora offers you links to buy the song you’re hearing through iTunes or Amazon.

Although you don’t have much control over the songs it plays, Pandora will help you discover new artists and double your song collection.