Starring John C. Reilly and Jenna Fischer. Rated 14A.

"No pressure!" ought to be the motto of Walk Hard: The Dewey Cox Story. After all, if you grew up in Shitville, Alabama, and were responsible for the death of your perfect brother and lost your sense of smell in the trauma, you'd have a lot to prove too.

You can tell from that description that this amiable spoof strolls along the lines already laid out in biopics of Johnny Cash and Ray Charles. And who better to play a man who manages to negotiate almost every phase of American pop music than John C. Reilly?

A rockabilly, R&B, protest-folk, psychedelia, and punk-rock Dewey Cox? You bet, and he does it all with a loyal band featuring needy bassist Chris Parnell and angry drummer Tim Meadows. Another SNLer is Kristen Wiig as his baby-making first wife, who is consistent in her lack of faith in his career.

Jenna Fischer is surprisingly sparky as Dewey's country-singin' second wife. Her Christian-infused S&M approach, however, isn't quite enough to keep him away from drugs, other baby-making women, or even large orchestras.

The humour, straight from writer Judd Apatow's laugh factory, as directed by cowriter Jake Kasdan (Lawrence's son), isn't as hard-edged as that found in Knocked Up or Superbad. But the filmmakers' have so much affection for the music and the movies they are spoofing that it hardly matters.

The songs are quite good, and there's plenty in the way of vintage guitars and amplifiers for gearheads. But Reilly, who is a real musician, and the filmmakers pull a clever trick at the end: they pile so many Hollywood-bio clichés into the last quarter that you start feeling nostalgic for a guy who never existed.