It isn't easy to pigeonhole Madredeus. The Portuguese group have described themselves as "semi-classical, a bit chamberish", with some jazz and world music too. Their roots are punk, garage and rock, crossed with native and South American musical traditions, and the mix certainly increases the intrigue. You could call this band Portugal's hottest export, but in more than a decade they have failed to make an impact over here. Now, perhaps, that's about to change. Teresa Salgueiro was the 19-year-old whose voice provided the raw heat for the band's initial fusion in late 1986. She and songwriter/ guitarist Pedro Ayres Magalhaes remain at its forefront 15 years and nine albums later, backed up by songwriter/synth player Carlos Trindade and guitarists Jose Peixoto and Fernando Judice.

A rash of applause broke out as Madredeus stepped forward, evidence of plenty of fans from the home territory. Salgueiro sings exclusively in Portuguese but this isn't a problem as long as you concentrate not on the words but on the emotions evoked by the music. (One glance at the translated lyrics on the new CD, Movimento, and you realise this band prefers the abstract to the literal: "She came from the mist/ Lost in kisses/ And confront/ And her electric face/ Her desire/ Can't see a solution.")

The mournful dreaminess of the set proved hypnotic, and Salgueiro's voice was extraordinary. When she sang higher notes it gained a sudden clarity, like a cloud dissolving against a fierce blue sky. She held top notes as carefully as a glass bowl and imbued longer lower notes with a thrilling fullness. And she clearly had fun making occasional introductions to songs in quirky English. One seemed to be "an invitation to travel in the regard of two laughing beans" - but that was probably just my hearing. The guitars ran in rills around her playful narrative, and at one point set up a Pachelbel-on-speed effect, to which Trindade added a trickle of church organ. The sense of contrast was heightened by the stillness of the guitarists and the fidgety light show behind them. The first set verged on the melancholic but the second was more energetic and more soulful, with Salgueiro adding a few dance steps to a stunning fandango-inspired piece. One ardent fan struggled from his seat at the end to present the diva with a bouquet of giant sunflowers, but there were times during this compelling set when it was hard to move a muscle.