Delays, Barfly, London

It's usually a doubtful move when a band opens with their most famous song; but not for the Delays, who launch with "Long Time Coming", their only Top 20 hit. It's hard to understand why the Southampton quartet aren't bigger; the brothers Greg (vocals, guitar) and Aaron Gilbert (keyboard, backing vocals) have boy-band looks and skinny black tops to match, and the music has commercial appeal. Could it be that they rock too hard for a pop band, but are too girly-pop to be indie?

Tonight's show calls out for a stage three times bigger – not least to accommodate the energy of their singer, who pulls shapes and leaps with his guitar. Greg urges the crowd to raise their hands – "We're corny like that." He's got a point. New single "Hooray" from the band's upcoming album Everything's the Rush is a feel-good radio-friendly track, if lacking in substance. But by the time we get to the beefier "This Town's Religion", which Greg (adorned with chunky silver necklace) dedicates to "chavs", much to the delight of some pint-wielding fans, they are rocking.

Their majestic pop owes much to the singer's superlative high-pitch vocals, as suited to emotive, vulnerable songs as to uplifting anthems such as "Love Made Visible" from their November EP, their first release with Fiction since they left Rough Trade. "Pieces", brittle, seeping with melancholy, shows their depth. It blends everything: Greg's opening intricate, mournful guitar-picking, the complex build-up of lush strings looped by Aaron with a powerful bass line from Colin Fox, and a guitar solo. That the strings sample was recorded by an orchestra shows their attention to musicality.

And the brothers make excellent harmonising partners. Even if Greg struggles with the high-pitched vocals of debut single "Nearer Than Heaven" from their first album Faded Seaside Glamour, you forgive him.

While the new material builds on the synth-happy pop, with the looped sample of "Keep It Simple" locking the song in the memory, it's the catchy techno-synth track "Lost in a Melody" that lifts the venue into a club vibe, setting the dance mood for the party track "Valentine" and the pulsating groove of the encore, "Panic Attack". When Greg says: "We're having a festival moment," the fans are too. Perhaps the new deal is the Delays' chance to make it to the mainstream.