“Walk Hard: The Dewey Cox Story” is a joke machine and a nice change from the better but almost uniformly downbeat movies out there this season. A biopic satire, it’s about nothing but its laughs. The songs may be good - well-made pastiches of various musical genres and eras - and John C. Reilly is wonderfully ridiculous as a lunkheaded music legend. But whenever the jokes begin to sag, and fortunately that’s not often, the movie has no reason for being.

It’s no stand-alone piece of work, either: If you haven’t seen “Walk the Line,” there’s really no point in seeing this movie. But those caveats aside, “Walk Hard” is 100 minutes of fun, and for pure, uncomplicated enjoyment, it’s the movie to see right now.