Knocked up hurriedly, you feel, in between Apatow's other projects, Walk Hard is the feted writer-producer's first fumble. As Spinal Tap's Nigel Tufnel might have put it, this one only goes to two-and-a-half.
The one area where 'Walk Hard' does manage to hold its own against classics of the genre such as 'This is Spinal Tap' or 'Sweet and Lowdown' is the music, all of which is expertly written and performed.
Apatow and director Jake Kasdan deliver a fair number of laughs, though nearly every good idea is pressed into service as a running gag. The biggest disappointment is their survey of rock history, which has all the depth of a Time-Life book.