Tenacious D, Secc, Glasgow <!-- none onestar twostar threestar fourstar fivestar -->

The genesis of Tenacious D's current incarnation has been even more lengthy than the career of their most famous member Jack Black, who first came to prominence via a show-stealing part in the 2000 movie adaptation of Nick Hornby's novel High Fidelity. Before that introduction to fame, he was a bit-part actor in American television and cinema, a period which included a spell alongside Kyle Gass in 1997's short-lived Tenacious D cable series.

Ironically, given that he was playing an amplified, caricatured version of himself, it was this role that would set the template for many of Black's most successful film parts to date, and one that he plays most convincingly in his band's recent debut feature, Tenacious D and the Pick of Destiny.

To describe "the D" as a side project would be to ignore the fact that Black and his musical partner, Gass, co-write all their songs; and beginning their UK arena tour with a near sell-out gig, even as their movie rides high in the box-office charts, suggests that things are going well for the duo. But there's also a suspicion that the joke has been spread a little too thin of late, given that Tenacious D were introduced to the world at large by way of their debut album five years ago.

Then, the concept - a pair of lunkheaded underachievers approaching middle-age, who are somehow (at least in their own minds) the unlikely core of the greatest rock'n'roll band ever - was fresh and funny, poking fun at the rock genre's over-reaching pomposity and delusion in the same way that Spinal Tap once did. But many of the attendant set-pieces for tonight's gig - challenging Satan himself to a "rock-off", egos splitting the band, Black's own over-energetic mugging and gurning - have been staples since as far back as the TV show.

Set against a backdrop of flaming red mountain peaks, the framing story to tonight's concert has it that the pair are in hell, having fallen victim to a domestic accident, and must confront Satan to go free. Their backing band consists of musicians disguised as Charlie Chaplin, Colonel Sanders and the Anti-Christ, with the latter and Gass driving the music on guitar riffs while Black fools and poses.

Among their scattergun selection of songs and narrative-propelling musical interludes lie the powering "Car Chase City", assisted by one of the intentionally poorest car chase effects ever, a dumb two-fisted paean to male bonding after Gass "quits" the band in "Kyle Quit the Band" and "Dude (I Totally Miss You)", and a deliberately twee sequence in which Black trips on shiitake mushrooms. The song "Master Exploder" is particularly amusing, as Black fakes the line "I do not need a microphone" and then stomps off-mic to deliver a bellowed mime to the recorded vocal track. "Satanic Milli Vanilli", he calls it. Older attendees might have also be amused by Gass's knowing "jam" - it is the riff to The Beatles' "And Your Bird Can Sing" - but how many younger fans would spot it?

The ludicrous finale, in which a hilarious, foul-mouthed Satan appears to claim Gass as a sex slave and must be repelled by Black, sure is stupid, overblown fun, while old favourites "Fuck Her Gently" and "Tribute" form a crowd-pleasing encore.

However, the set-closing presence of The Who's "Pinball Wizard" proves the point that the most astute rock acts can poke fun at themselves with much more verve than two portly film stars will ever manage. The joke's still amusing, just, but it's in need of an update before a farewell tour becomes a necessity.

Touring to 19 December ( www.tenaciousd.com)