How many songs do you have in your iTunes library? 1,000? 2,000? 5,000 or more? If you’re one of those people that never has enough music in his or her collection, then today’s software pick, The Filter, is for you. The Filter is a utility that works with iTunes and, ideally, a broadband Internet connection to add a few new wrinkles to music listening on your Mac.

Created by the U.K.-based company called Exabre Limited with backing from such notables as Peter Gabriel, The Filter is a free download for both Windows and Mac (which is Universal Binary, good for both PowerPC and Intel Macs).

It does several cool things with your music collection:

Automatically generated playlists: If you select several songs from your collection (Tip: hold down the Apple key while you click on songs with your mouse), The Filter will generate a playlist of similar songs (a jog wheel at the bottom of the window lets you control the number of songs selected). You can tell The Filter to base the playlist on the songs, the artists or the genre. The new playlist appears under your Playlist header in iTunes like any other, and will transfer to your iPod the next time you sync it with your Mac. You can have endless fun selecting odd combinations of songs just to see what the software comes up with. Picking three alt rock songs from the 80s generates a list with other alt rock songs from the 80s. Mixing up musical genres generally results in schizophrenic playlists, but the bizarre juxtapositions can put a fresh perspective on old songs. It’s a bit like the iPod’s Shuffle function, but with more control. You can use The Filter's window at the bottom of your screen to control the currently selected playlist, pausing, playing or skipping songs without going back into iTunes. The Filter even uses iTunes’ album cover art.

Discovering new music: Clicking on "Discover Music" in the sidebar of The Filter’s window brings up a list of recommendations of other music you might like. Double-clicking on one of the songs in the list directs you to the iTunes Store page where you can preview and buy it, if you like. Better yet, if you repeat the process you’ll get a slightly different list of recommendations. This feature could be dangerous to your wallet.

Artist info: My favorite feature is the Artist and Album Information option, also selected from the sidebar in The Filter's window. In addition to showing the basic stuff -- the name of the song, artist and album along with its cover art -- this feature uses your Internet connection to fetch a series of info tidbits about that artist and album from The Filter Web site. It reminds me of that old VH-1 show, Pop-Up Video, except the sort of nuggets The Filter displays are more in-depth. It reads like a hip encyclopedia seasoned with a smidgen of trivia. If you have a lot of artists in your collection, expect to waste countless hours on this, particularly since it provides distinct data for each album, rather than just a generic set of entries for each artist.

The Web connection: If you go to The Filter Web site and create an account, the software on your Mac connects with the Web site and delivers a heavier dose of the same features, plus a few new ones. When you go to the My Filter page, you’ll see an assortment of elements relating to the artist you’re listening to. To the left is a list of recommended artists, with links to both the iTunes Store and Amazon. In the center is information and photos, including a bio of the artist and an album review. Below that is a window showing more albums by that artist. Clicking on an album changes the album review information in the section above. To the left is a “Wishlist” where you can store lists of music you plan to buy, and a Playlist widget, which can store Playlists that The Filter creates (a button on the control strip widget transmits Playlists to the Web site). Below that is a list of the top five You Tube videos (rated by popularity) featuring the selected artist. Awesome!

Caveats: All that said, The Filter has a few drawbacks. The worst for me is that it’s a CPU hog, slowing down my entire system. This could partly be due to the advanced age of my 867 MHz G4 tower, but still. I also encountered some quirky behavior; for instance, it periodically failed to bring up an iTunes Store page. Trying again sometimes rectified the issue, but on a few occasions I had to restart the program to get that feature to work again. To be fair, The Filter is a free and in many ways experimental piece of software, so perfection cannot be expected. It is definitely worth checking out.

UPDATE: Just my luck... they updated this software this morning, so the interface is a bit different. I've revised a few sentences in my review to reflect the changes and updated the screen shot as well.

UPDATE 2: Eoin Norris, a member of Exabre's Mac team, e-mailed me today to thank me for the review and noted that some of my problems coulkd have been related to my old graphics card: "

We have added some cool and snazzy features ( unfortunately I didn't notice that the Now Playing Core Image image manipulations did not work on lower level cards until just before release : we will fix that this week).... Also you can switch between the new version and the older (smaller) player by clicking the green maximise button."