Acoustic gigs are daunting affairs. Closer in mood to a church service than a knees-up, they elicit austere appreciation rather than provide whole-hearted entertainment. Heads nod, hands clap but feet stay firmly on the floor. So it's a surprise to see moshpit-friendly Scots Idlewild embracing such solemnity, as singer Roddy Woomble admits. "There's been a strange reaction from band and audience," he says, referring to the whistle-stop acoustic tour. "But it's getting better."

Much has changed in Idlewild's world since the release of The Remote Part in 2002. The band have a new bassist, Gavin Fox, and guitarist, Allan Stewart. Woomble has relocated to New York but recorded the new album, Warnings/ Promises, in Los Angeles. It reveals a new maturity in Idlewild's melancholy sound, and especially in Woomble's voice. Where once he squeaked and shouted, he now has depth and assurance.

Flanked by fairy lights, lampshades and rugs, Woomble acts as a shaggy-haired MC of what looks like a cross between a cosy night in a student bedsit and the dying moments of a sedate garden party. But he is an increasingly confident pop star. While a violin adds grace to the repetitive lyrics and frustrated rhythms, Woomble grasps the microphone with a desperate intensity, as if trying to make up for the absence of the sort of energy that usually marks Idlewild shows.

Yet although the acoustic versions of Little Discourage and When I Argue I See Shapes reveal the sensitivity behind the teenage angst, they demand punk-rock participation. Later songs, including You Held the World in Your Arms and the new single Love Steals Us From Loneliness, fare better: they remain anthemic despite the naked arrangements. Still, the impression that Idlewild are trying too hard to prove themselves - which is helped by the inclusion of songs by Ben Harper and folk guru Vashti Bunyan - dulls their daring to be different.