The party for Ogun Records' 25th anniversary was also a celebration of a way of playing jazz. In a long jam session that brought together many players with ornery personalities, big techniques and a suspicion of too much preparation (Louis Moholo, Keith Tippett, Phil Minton and Julie Tippetts among them) free improvisation was almost obligatory.

It was a fitting backdrop against which to consider Ogun's achievements. Tuesday's powerful contributors included pianist Keith Tippett and singer Julie Tippetts, with Paul Rutherford on trombone and the redoubtable Louis Moholo on drums. From stuttery improv tiptoeings, a ramshackle spontaneous counterpoint emerged as Julie Tippetts's yelpy interjections were underpinned by Rutherford's dark trombone lines, and Keith Tippett's initial reserve intensified into bursts of flaring arpeggios.

A bigger group that included trumpeter Harry Beckett and Eddie Prevost on drums swelled exuberantly from a chanting, late-Coltrane incantatory sound into a driving jazzy swing that Prevost (usually a free drummer) gleefully delivered as if he did it every night.

A duo set of extraordinary vocal acrobatics featuring singer Phil Minton and pianist Veryan Weston reaffirmed Minton's rare mix of pub-singing bravura and instrument-mimicking agility. More of the duo's music was written, but it didn't dampen anybody's fires.