Those who felt Jack Black hit the right note in the plank-spanking comedy School of Rock could find themselves in tune with his latest musical adventure.

Building on the genuine cult following of his band Tenacious D, Black and co-writer and star Kyle Glass have dreamed up the band's meandering climb from humble beginnings.

We first meet a junior JB (Troy Gentile) screaming profanities to an acoustic guitar accompaniment as his horrified parents - including bible-bashing dad Meat Loaf - look on.

His ass whupped and sent to his room, JB beholds a burning vision of rock god Ronnie James Dio who tells him to head for Hollywood and "find the secrets of his art".

Hooking up with Venice Beach troubador Kyle Gass, they form the band Tenacious D - and set off on a Lord of the Rings-style quest for the "pick of destiny" - a guitar pick carved from satan's incisor that will give them the edge in Open Mic night at Al's Bar.

The plot, as you can probably deduce, is not the most compelling reason for watching. The main draw is Black's unforgiving eye for the pomposities of heavy rock.

Yet his tone is never vicious and it's this affectionate mockery of the form that provides the humour, although this tends to be of the titter rather than the belly-laugh variety.

Highpoints include a mightily impressive bit of scat-singing from Black as a fret-melting Gass wring's Bach's Bourees in E Minor from his acoustic guitar.

A couple of cameos - from Ben Stiller as a muso acid casualty and Tim Robbins as a mysterious Eastern European seeker of "the pick" - also add value, as does Ronnie Jame's Dio's effervescent perm.

The beauty is in the detail...and for those about to rock we can do nothing but salute you.

Tim Evans