It's the politest crowd of all time. People move out of the way without me asking them to. One skinny guy, wearing glasses and a cardigan, apologises for no discernable reason. This isn't surprising. Nice people generally come to the Luminaire. Normally to watch nice men play quiet acoustic guitars, nicely. A bit like Gravenhurst's first record Flashlight Seasons.

The first shock for anyone whose only involvement with Gravenhurst being Flashlight Seasons – an accessible, downbeat folk album – is that this is not just that one guy. It’s a four-piece ensemble onstage. Singer Nick Talbot wears earplugs, unnecessarily. He makes some Slint-y harmonics on his electric (!) guitar. Alex Wilkins on other guitar echoes it with warm swathes of gentle noise. The rhythm section is pounding, concise and unrelenting.

This is unsettling. Gravenhurst's four excellent albums sound markedly singular, the product of one brain. But the band’s performance is crucial to their live sound; the instrumental moods build up, develop and fade. Talbot’s voice, when it finally arrives after a drawn-out jam, is fey and resigned. His voice is often the band’s main draw on record, but live it's not quite translating. On The Velvet Cell, Talbot's a pissed off computer techie, singing about murder "lying dormant in the heart of every man" with a touch too much passive relish. It's great, but the harmonic guitar stuff at the beginning of the set led the songs better than his paper-thin voice, which was weedier and shyer than it should be.

The second shock is the music. It's hard to think of a neater, more comfortable niche than "that band on Warp who do the quiet folk thing," but to their credit Gravenhurst have moved closer and closer to total psych noise mania with every release. Hollow Men from new album The Western Lands is total Dinosaur Jr territory, without the solos. Talbot strums his guitar manically, making his right arm look like a crazed, live side of ham.

They get called "post rock" a lot. I guess that's fair. The quiet parts are inventive and fluid. The loud bits are rocking, not revolutionary, but totally worth the wait when they arrive. That's about the biggest plaudit I'm ever likely to give "post rock". But it sounds more like bastard Kraut to me, anyway.

Occasionally the strumming, feedback, fragile voice and layered drums catch alight and it feels like everything is beautifully interlocking. Except, you know, in a non-stoned way. Talbot's voice warms up and becomes the beautiful counter to the instruments' tired, reliable funeral song. It’s weirdly welcoming, but it wasn’t what I expected.