In the right hands, music can be a fine art. In Monet’s, it’s a bit of a dog’s dinner – less nuance and careful dabs of colour and more a blank canvas aggressively splattered Jackson Pollock-style in the hope that something takes shape. That comes closest to happening on closer Wallace, a messy ruckus that melds Mclusky and System Of A Down.

My Octopus Mind’s USP is a double bass player – an unusual sight on stage at the Moon, to be sure. Unfortunately, they don’t have many other SPs. Twitchy, protean, jazzy/mathy rock is tricky to get right, its short attention span often mirrored by the audience’s, and – despite evident musicianship – the Bristolians’ particular brand bewilders and grates more than it dazzles. At least they, like Monet, have the good grace to save the best for last, stirring up a minor frenzy in the front row.

In his burgundy pyjamas and slippers, Tom Adriaenssens looks like a fatigued and apoplectic flat-owner who’s climbed out of bed and come downstairs to complain about the noise. It turns out that he’s actually the frontman for headliners The Guru Guru (not to be confused with longstanding German Krautrock outfit Guru Guru, no definite article), and Where’s My Rum (Is It Anywhere) is a song, not just him stumbling about trying to lay his hands on a misplaced beverage. “I’m in a good place, man,” he insists, increasingly less convincingly, stood on a plastic crate that lights up with a stamp of his foot.

Later, on (In) Snakes & Ladders (Stakes Don’t Matter), Adriaenssens claims “I’m a reasonable guy” while also declaring “I’m going full denial”. What’s he done? Bug-eyed and grinning like Jack Nicholson’s Jack Torrance, he could be capable of anything. Much like Les Savy Fav’s Tim Harrington, Adriaenssens is a magnetic presence you can’t simply take your eyes off, a manic street preacher putting words to his band’s jerky, weird post-punk. His sugar-coated American accent makes The Guru Guru sound curiously like stadium-scale superstars gone spectacularly, splendidly wrong.

Evidently used to bigger stages in their native Belgium, they’ll be back in the UK in August to give the audience at ArcTanGent festival a taster of forthcoming album Make (Less) Babies. Its title sets my teeth on edge grammatically speaking, but the new songs – and tonight’s performance as a whole – suggest that The Guru Guru will soon have a whole load more disciples.

The Guru Guru, My Octopus Mind + Monet, The Moon, Cardiff, Wed 12 Apr

words and photos BEN WOOLHEAD / header image EVA VLONK