Each night this week Letterman has a musical guest perform a musical tribute to the Beatles. Two nights ago Lenny Kravitz did an amazing version of Get Back. Last night the Flaming Lips, joined by Sean Lennon, did Lucy in the Sky, which wasn't as good. Lauryn Hill performs tonight.

Of course, Letterman is hosting the Sunday night special on the Beatles with many special guests, including Stevie Wonder, whose version of We Can Work it Out is the best Beatles cover I've heard.