Iceage frontman Elias Bender Rønnenfelt stands on the security barrier at the front of the stage, oblivious to the strand of rope dangling from the ceiling, which brushes against his face. Then he crouches down, singing directly at the rows of adoring, air-punching fans, for whom the height of delirium seems to be to touch the hem of the Danish singer’s garment. Then Rønnenfelt recoils backwards while, at either side, the band’s guitarists keep their heads resolutely down, although they have presumably learned to keep a sly eye on the flailing vocalist, lest he knock one of them out.

Performances such as this have earned the Copenhagen quartet a cult following in the last three years among people who are perhaps seeking a slightly deeper level of angst than some of the band’s peers. Rønnenfelt’s exertions are undoubtedly a schtick, but he seems genuinely disaffected and misanthropic. Here, though, it’s hard to make out the lyrics, which range from simmering expressions of alienation (“There’s a vile fury within us, despite what you’ve been fed”) to a peculiar diversion about feeding an animal with champagne.

The band’s recent album, Plowing into the Field of Love, saw them transcend their hardcore roots into the raucous post-punk of Nick Cave’s Birthday Party and the early Fall. Drinking-by-gaslight anthem Abundant Living has a hook worthy of vintage Pogues, but, minus the more lavish instrumentation of the recorded version, here seems somewhat thrown away.

In fact, for all Rønnenfelt’s efforts, he sounds hoarse and looks tired, and the brisk performance has an unexpected going-through-the-motions feel, as if the band’s relentless gigging and quest to progress beyond smallish venues is starting to wear them out. He says nothing beyond an abrupt “thank you” and after just 40 minutes, places the microphone down and those adoring fans simply walk away.

• At Liverpool Sound City festival on 22 May. Box office: 0151-558 0422. Then touring.