Generations of music teachers have tormented their reluctant pupils with the mantra "practice makes perfect" but The Bays challenge that idea.

Despite being one of this year's hottest Festival tickets, this fourpiece dance act never practice. Before they perform, they don't even discuss the playlist.

Everything they do on stage is unplanned in order to create a unique audience experience. "If you don't rehearse, you play with fresh enthusiasm every time you start," says keyboardist Jamie Odell.

The band's approach to the dance music genre is refreshing and their shows take the form of a single piece of improvised music.

Drummer Andy Gangadeen and bassist Chris Taylor create a rhythmical heartbeat over which the inventive Jamie and Simon (palmskin) Richmond layer sounds using their keyboards and an Apple Mac.

The effect is a performance which can veer from ambient through hip-hop, disco and electro punk to roof-raising drum 'n' bass. Every few minutes, the flowing music evolves into something different in much the same way as a set mixed by a DJ.

The Bays first came together for a one-off gig in London in November 1999. An immediate success, they were booked for more shows.

Since then, they have gone from strength to strength, becoming regular fixtures at festivals all over Europe, from Glastonbury to the Eurosonic Festivals in Holland. Last year, they had a sell-out weekly residency at the Jazz Cafe in London.

Despite their success, the band have no intention of releasing any recorded material except downloads of their gigs available free from their web site.

The band pride themselves on entering a "creative partnership" with the crowd, receiving feedback from the dancefloor and constantly reinterpreting that response.

They argue that a recording would only represent a fraction of the total Bays experience. For them, "the performance is the product".

All four players have other musical lives. Work for the Spice Girls apparently paid for the door knobs in Andy's house. Chris works with anarcho-punks The Poison Girls and his session credits range from Spiritualized through to Simply Red.

Simon is a highly regarded producer, experimental musician and DJ. Jamie is better known by the aliases "Jimpster" and Audio Montage. Together are one of the best live bands in the UK.

The Bays are joined in this Festival exclusive by Burnt Sugar, a 15-piece troupe of non-conformists led by New Yorker Greg Tate.

Burnt Sugar fuse Miles Davis, Sun Ra, Chaka Khan and Jimi Hendrix in a gloriously unfettered and infectious freefall of improvised music.

These two bands share a spontaneity which sets them apart from other music acts. Their bravery allows them to experiment and explore and by doing so, create those wonderful mistakes which only come through improvisation.

Expect the unexpected.

Starts 8pm, tickets £14.