First, disorientation; then, redefinition. Lime green and white strobe lights stutter across five busy silhouettes, slicing their movements into nanosecond jump cuts. Then a deep blast of synth bass drives home the point that Fontaines DC – a band once so defined by their home city that “Dublin City” is engraved into their name – may no longer be the Irish literary post-punk rabble-rousers that fans have grown to know over the past five years. Fontaines are still indelibly tinged with emerald, but now it’s a more lurid, palate-stripping shade, one not a million miles from pop maven Charli XCX’s brat green.

This moody assault on the senses resolves into Romance, the title track of Fontaines DC’s fourth album, released days earlier. Low-slung and menacing, it sounds a little like Depeche Mode – a kinship underlined by singer Grian Chatten’s doomy intonation (“Into the darkness again,” he sings). Post-punk to stadium goth is no vast leap, but it’s worth noting that Romance producer James Ford’s lengthy CV includes not only Arctic Monkeys – the band to whom Fontaines DC are most often compared in terms of positioning – but Depeche Mode’s most recent work.

The new influences don’t stop there. Across 45 minutes, Fontaines DC will perform a whistlestop tour of breakbeats, Nirvana and Pixies basslines (Death Kink), nods to Smashing Pumpkins, dreampop and slacker rock (Favourite), playing all new tracks bar two old songs. The band’s latest album not only strikes out on these fresh paths with a new producer, but it’s all happening on a different label as well – the venerable British outlier XL (they were on Partisan Records before).

So: all change. If Dogrel, FDC’s debut album, nodded to Irish verse, and A Hero’s Death (2020) and Skinty Fia (2022) examined the band’s own émigré status, Romance heaves anchor geographically and reorients them into a state of mind: sometimes wistful, sometimes brutal (Death Kink is about an abusive relationship). “Maybe romance is a place,” croons Chatten (who also released a very good solo effort, Chaos for the Fly, last year).

This is the early evening matinee of a two-set night in south-west London, part of a low-key rollout for Romance before a full-size tour later this year. We’re in a very small venue, but Fontaines DC’s intentions are writ large: grow the band, but sideways as well as more obviously upwards. “Deep within and far without,” as Chatten told an interviewer last spring. Depeche Mode apart, Fontaines seem to be gravitating towards the pockets of old American music currently in vogue, and largely regurgitating these influences with a distinctive Fontaines stamp.

It’s going swimmingly so far. Having toured in Europe over the summer, the band’s recent Reading and Leeds festival sets could be seen as promising auditions for eventual headliner status, the “next Arctic Monkeys” guitar band role currently being contested (amicably) between FDC and Idles. These bijou gigs are probably the last time for a while that fans will be close enough to see the glint of Chatten’s diamante-embossed socks.

Not all of Romance seduces tonight – the live debut of Sundowner, sung by guitarist Conor Curley, is more lugubrious than you’d like – but a handful of tracks do reveal fresh detail in this live airing. The granular matters, because if the shouts tonight are most often “I love you Grian!” (or “free Palestine!”), Fontaines DC’s other members are no slouches in terms of firepower.

The whole band’s transition from scrawny to saturated is convincing. The guitar tones on Here’s the Thing – not exactly muted on the album recording – gain a welcome sourness in person. The assorted six-string groans on In the Modern World provide a counterpoint to Chatten’s couplets. From the title on in, the track is an audible bid for epicness, albeit offset by some cool Lana Del Rey-style ad libs.