The film opens on a rock band - Vesuvius - closing a set. They finish and are offered a contract on condition that they get rid of their drummer Robert 'Fish' Fishman, replacing him with the record label owner's son. Although they don't want to do this they are quickly persuaded to do so. The drummer is understandably upset.
Cut forward 20 years. Vesuvius are a world phenomenon, and have just released yet another massively successful album which they are now touring on the back of. 'Fish' is working in a call centre. He quickly loses this job when a colleague plays the new album and he reacts...quite badly. We find out that this is not the 1st time he has lost a job through issues arising from the band. On this occasion he also loses his girlfriend and has to move in with his sister and family for a while. From here he eventually agrees to help out his nephew's band by filling in for their drummer at a prom gig. From here we follow the rise of the band and Fish's fated confrontation with Vesuvius.
It's a comedy, and a very simple one at that. The jokes are as often as not slapstick and when not don't require too much thought to grasp. The acting is acceptable, the various cast members deliver their lines nicely enough but nobody is being asked to portrayal great depths of emotional turmoil. The songs are original and pretty good, although that of course is a matter of taste. They aren't spectacular and they don't get stuck in your head for days afterwards which is a bonus. Overall this is an ok film with some nice lines, but there are better rock films out there. If you like it you might want to take a look at School of Rock, (which has a similar plot), Still Crazy, or This is Spinal Tap.