No matter what, last night's "American Idol" contestants couldn't say they had weak material; the songs were all from the songbook of the iconic Beatles -- in particular, legends Paul McCartney and the late John Lennon.

These are some of the best-known songs -- and performances -- in American rock 'n' roll music.

But it was a challenge nonetheless: Do they stay with the original songs' styling and arrangements, which are carved into music lovers' memories? Or do they push the envelope, as the judges often urge, but risk corrupting a beloved classic?

The judges were pretty easy-going on this classic musical turf, although Andy Garcia's "Money Can't Buy Me Love" didn't work for any of them. Long-haired rocker Casey James, on the other hand, drew raves with Lennon's lazy "Jealous Guy," leaving judge Simon Cowell "very, very impressed."

Irish American star Siobhan Magnus, performing in the last 30 minutes of the two-hour show, picked the lesser-known but angelic "Across the Universe." The Lennon-written song first appeared on the charity compilation album "No One's Gonna Change Our World" in 1969, and later, in modified form, on the Beatles' final album, "Let It Be."

Randy Jackson thought it was a little "sleepy," but loved the "tender side" Magnus showed. Ellen DeGeneres loved the song. Kara Dio Guardi enjoyed the change from Magnus' "belting" songs of past shows, and Cowell enjoyed the style change as well.

All in all, Siobhan took a big risk and made it work!