By Michael Slezak
Updated May 05, 2010 at 04:00 AM EDT

When you can find full studio versions of every top 10 contestant’s performances on iTunes, it seems almost quaint to release a compilation CD that pretends fans of the show wouldn’t opt for an á la carte approach over this pupu platter of wildly varying quality.

Sure, Crystal Bowersox’s goose-bump-?inducing rendition of ”Me and Bobby McGee” is a must-have, while Lee DeWyze’s ”Treat Her Like a Lady” adds gruff urgency to the Cornelius Brothers chestnut. And two other standout performances from the Idol stage — Siobhan Magnus’ dramatic reading of ”Paint It Black” and Casey James’ sparse, Bob Seger-esque ”Jealous Guy” — translate nicely as full-length recordings.

But unless there are parts of the country where listeners cannot purchase albums by the Beatles, Aerosmith, or Chris Brown, what possible function is served by the follow-the-bouncing-ball karaoke of Katie Stevens’ ”Let It Be,” Aaron Kelly’s ”I Don’t Want to Miss a Thing,” or Andrew Garcia’s ”Forever”? Meanwhile, no note goes unpunished on Michael Lynche’s overwrought version of India.Arie’s ”Ready for Love.” At least there’s a morbid-curiosity factor with Tim Urban’s emotionally vacant reggae interpretation of the Rolling Stones’ ”Under My Thumb.”

The one revelation here is Didi Benami’s acidic, raspy twist on the Stones’ ”Play With Fire.” The perpetually weepy 10th-place finisher may not have been cut out for the pressure-cooker Idol stage, but she’s right at home in a recording studio. C+