Madredeus is an international phenomenon, with a big, largely non-British following for their ambient world-folk. Thursday's concert, kicking off the Atlantic Waves festival of "exploratory music from Portugal and beyond", attracted plenty of fans who demanded two lots of encores from their heroes.

The quintet's sound dates from a time when rock'n'rollers who were too young to die chose New Age instead. Madredeus's dreamy mix of fado and pop chord sequences with the glassy, classy voice of Teresa Salgueiro sold records by the bucketload. Most of the original members have now departed, leaving Salgueiro and guitarist Pedro Ayres Magalhaes with three newer recruits. Nevertheless, the keyboard sounds used by Carlos Maria Trindade don't seem to have been upgraded since 1986.

A typical Madredeus song is slow, with cloying synths over undulating classical guitars and bass. There are occasional chinks of imaginative light, but these are undermined by soggy digital piano parts and synth pads. Vislumbrar - O Canto Encantado has moments that are cinematic and touching, but it's also boring.

Even the more upbeat Adoro Lisboa - one of several songs of praise for their home town - is sabotaged by an annoying keyboard sample that even Pete Waterman would have vetoed. Maybe Madredeus are just like rock'n'rollers - trapped in a formula that no longer works, but guarantees ticket sales as they haul their slick show around the world.

The remarkable Salgueiro soars gracefully over her bandmates with a clear, reedy voice that is controlled, pitch-perfect, yet emotional. She deserves better - from Portugal and beyond.

· Atlantic Waves 2006 continues until November 30. Details: 020-7908 7622.