London Improvisers Orchestra, Warwick Arts Centre, Coventry <!-- none onestar twostar threestar fourstar fivestar -->

The London Improvisers Orchestra don't get out much. This was their first performance outside the capital, doubtless due to the unwieldy nature of a group whose ranks often swell to 40 or so. The excuse for a day trip was an invitation from Shifti, a four-day festival of improvisation in music, dance and theatre.

The LIO performs on the first Sunday of every month at the Red Rose pub in Holloway, and their roots lie in a 1997 Contemporary Music Network tour by the US bandleader Butch Morris. His technique involves an organised form of improvisation, where arcane hand-signals prompt instant responses. While the LIO is made up of fiercely individual players, their aim in this setting is to be at the service of the entire sound.

This evening presented four improvisations that would blend into a seamless stretch of music, with the conductors of each section stepping out of the ranks. Caroline Kraabel, Phil Wachsmann, David Leahy and Dave Tucker downed instruments and spent about 10 minutes each demonstrating the imaginative reaches of spontaneous composition.

Kraabel uses a flower as a baton, and sweeps complex waves of silence across the trumpets, trombones, saxes and strings, grouping sonic permutations and signalling volume curves and sudden stops. The orchestra is mostly without amplification, apart from Tucker's guitar, Adam Bohman's table-top junk-pile and the fuzzy electronics of Pat Thomas. It's a joy to hear the fast-reacting reeds, horns and tumbling percussion, unimpeded by mics but raising their voices through sheer numbers.

Leahy's section was the most dynamic, impressive in its physical abandon. He invoked the walking symbol up his forearm and set the two trombonists perambulating about as rasping circus clowns. The trumpets followed, and suddenly most of the orchestra was wandering loose, climbing the stairs or blasting horns from the balconies.

Tucker's piece began with icy string textures, then jumped into a thunderingly primitive rock rhythm, with Thomas feeding in bursts of electronic scurf.

The final piece was a collaboration with other Shifti performers, conducted by Rex Hossi Horan and featuring a team of physical theatre performers.

Tension was generated throughout, and the result is a sense of continuous surprise, of danger only narrowly averted.