Conspiracy theories abounded in the concert hall when the award-winning quintet Empirical appeared as a quartet.

Drummer Shane Forbes and bassist Tom Farmer were present but vibist Lewis Wright had replaced pianist Kit Downes, and of trumpeter Jay Phelps there was no sign. “Kit and Jay have gone,” confirmed an otherwise tightlipped publicity person.

Under the circumstances, Empirical’s tribute to Eric Dolphy went remarkably well. Nathaniel Facey had written clever originals in Dolphy’s style and took formidable alto-sax solos, while Wright helped recreate the ambience of Out to Lunch, an album Dolphy recorded with vibist Bobby Hutcherson.

Courtney Pine had promised a tribute to soprano-sax legend Sidney Bechet but fans were relieved to find his show basically unchanged, with lengthy instrumental tirades from the leader, each rising in intensity to a circular-breathed shriek.

The first of these technical exercises was exhilarating, the second and third progressively less so, the fourth sheer torture.
Sadly, some gifted sidemen, violinist Omar Puente and pianist Alex Wilson, began aiming for similar fireworks, too. Hats off to guitarist Cameron Pierre, the one artist who preferred keeping it musical.
Until Sunday (londonjazzfestival.org.uk; bbc.co.uk/radio3).