Free improvising is - and listening to it should also be - an experience in conviviality. Most forms of expectation and structure are set aside in the interests of what is essentially a sonic conversation where even the etiquette of dialogue is intermittently dispensed with so that individuals can indulge in moments of monologue, interrupt and overlap one another or even remain silent. The result can be a musical exchange of startling depths and freshness.

Oxford Improvisers is an organisation of performers and composers from a variety of musical backgrounds who regularly get together for this free and convivial exchange. On Saturday, March 17, they are giving a landmark performance in the Jacqueline du Pré Music Building with guest soloist John Butcher, a saxophonist known internationally as a player of great power and imagination. His latest album has been described as "an essential document".

The evening will include both a solo performance by John Butcher, small group performances with other members of the Oxford Improvisers and a number of pieces played by the full Improvisers orchestra, which includes a remarkable cross-sections of musical talents. Professional orchestral oboist Nicholas Benda, who might otherwise be performing Handel in the Albert Hall, says: "I will be setting aside my dinner jacket, polished shoes and written score to take part in an event where the rules are redefined so there is no wrong note and also in some sense no right one either. The quest for sudden perfection is always on."

Alongside classical players, the Improvisers orchestra includes such diverse talents as Malcolm Atkins, who has composed for Radio Four, Chris Stubbs, using a battery of percussion, including many found objects, and Pete McPhail, a flautist and saxophonist, who has been a leading light in the world of free jazz for many years. The performances - organised by cellist Bruno Guastalla, himself a highly original composer - begin at 7.45pm and tickets are available in advance from www.wegottickets.com. This is a very special event in the musical calendar of the city and a welcome contrast to a diet of classical greats'.