My friend and I meet just as the doors open: scurrying into the empty venue, we fork out £6 for a beer each and nestle ourselves up against the railings. Bricknasty bring a sound straight out of Ballymun and are quickly becoming one of the most sought after live acts around: we want to be close enough to hear it all. Lying across the stage, catching the orange half-light of the Village Underground, is a tuba.

London’s oreglo are the openers. I’ve been lucky enough to see them four times: the trio discard genre like it’s nothing. In their unique formation – electric guitar, drums and tuba – they set out to capture London sound: it’s eclectic, diverse, chaotic, and always breathlessly cool – the sounds of futuristic jazz bend into metal with a touch of Zeppelin, brought back with a smattering of spoken word. They’d been playing in Cambridge the night before. The drummer, Nico, whips the snare into a broken backbeat, diverts it into swing; the hands of Linus Barry dart up and down the fretboard as if shredding sheer electricity; rippling up from underneath, the tuba, empowered by Teigan Hastings, produces an overwhelming, ribcage-rattling sound, forcing itself into the corners of the room. Not many people in the audience have seen a tuba solo before, they rock back and forth wide-eyed.

In the intermission’s darkness, two stagehands feverishly assemble the most complex drumkit I’ve seen in a while: five cymbals, two snares, four toms, cowbells. Against a backdrop of an Irish folk tune, Bricknasty walk out into the darkness. As the lights come up, Fatboy – their anonymised lead singer and guitarist – emerges, black and white balaclava on, a small brown hat, wreathed in an Éirinn go brách flag. The crowd roar. There’s no time for pleasantries. The band launch into their first track with feverish intensity, an intensity I think they can’t possibly keep up for the rest of the gig – they do.

“Music seems to have possessed him, ordered each of his limbs to do something different”

Drowned in the lights of the Irish tricolour, Fatboy’s hands emerge from the folds of the flag and wind themselves up and down the fretboard as if they’re pint-pointedly programmed to perfection: stringing together licks I didn’t know could be played, contorting themselves into chords I didn’t know existed. Except I know they’re not programmed, it’s all beautifully human: he comes close to rhythm and swerves, swinging away, toying with the time of his audience. After almost every note he zealously works his whammy bar, radiating his last played note out upon the airwaves.

When he’s not playing guitar, his hands disappear beneath the flag’s wings and he almost shudders – music seems to have possessed him, ordered each of his limbs to do something different: he’s singing into the mic with a voice that releases nigh-angelic vibrations punctured by squeals and screeches, proudly demonstrating his uncanny vocal range interspersed with moments where the feeling takes over.

“Alternating between the sublime and the frenzied: that’s where Bricknasty excel”

I’m equally bewitched by the drummer, Korey Thomas: he cradles his sticks so delicately, like paintbrushes, before scattering them across the drumset, switching subdivisions in the blink of an eye. One minute he’s laying down a slow-stomping backbeat, the next he’s torturing the bell of his ride cymbal into a heart-palpitating fever before spilling out across the entirety of the kit with a fill like a wave that keeps breaking. Bringing his stick down hard against the rim of his snare he shatters it in two. Glancing at it indignantly, almost ashamed of its weakness, he flings it into the air: it ricochets off of one of the glass skylights and lands right at my feet. Meanwhile, Fatboy’s hands seamlessly spider up and down his guitar like figments of pale light, devouring scales with ease, spilling out melodious chords in soul-shearing swells.

Alternating between the sublime and the frenzied: that’s where Bricknasty excel. I realise that I’m constantly unsure of how to move, constantly and continually surprised. In the frenetic speed of their set they architecture millisecond-perfect pauses: they wait for the audience to raise their hands to clap or whoop and descend back into the next bar. I try to dance but I’m not sure how – half of me moves to the rhythm of the drums and the other is pulled by the riddles of the guitar; then the alto sax rises up from the dark sonic undergrowth, the computer samples, the tenor sax, a shuddering bassline: I’m almost paralysed, shivering and jolting along with Fatboy. I don’t know what’s going on but the sweat feels like bliss.

“After such blood-thumping frenzy, we all sway in silence, shrouded in blue light”

Then: a break. Only with Bricknasty do you get a three-minute hiatus for craic. Water bottles are emptied, compliments handed out: “Your moustache’s grand, don’t you think his moustache is grand?” “Yeah, stunnin.” The drummer completes. “Great jawline too, you’re making me insecure.” We laugh; we forget that minutes ago he had us all under control like the zombified masses we are.

It doesn’t stop, however. It never stops. The rhythm guitarist plucks his high strings and then modulates them with the volume knob on his guitar, his notes become sirens. He samples Fatboy’s shrieks and amplifies them, echoing across the bare-brick walls of the Village Underground. The carotid artery of the saxophonist as he tortures out the finale of his solo verges on bursting. Flights of intricately-architectured improvisation layered on top of instrumental mastery, played off as chaos. Fatboy leads some classic call-and-response. At moments it feels like a singing lesson, but it mostly feels transcendent: hands are raised, he leads a murmurous mantra of “thank you, lord” that swirls around the venue.

Then the crescendo. After pointing to the flag earlier in performance, Fatboy tenderly asks: “Who loves Ireland?” So much noise meets my ears. The lights die down, and Thomas produces a tin whistle. They begin ‘is é a locht a laghad,’ an idiom loosely translating to ‘the fault is that there is so little of it’. After such blood-thumping frenzy, we all sway in silence, shrouded in blue light. The tears begin to prick. How does this voice at once enliven folk roots as well as deliver unflinching social commentary straight out of Ballymun? Whatever Bricknasty has in store next, the world isn’t ready.