For 60 years, the flowing countermelodies of Jimmy Blanton, Duke Ellington's shortlived young double-bass genius, have practically run the bass show. Now comes Renaud Garcia-Fons, the astonishing French-Spanish virtuoso who has rewritten the score all over again. Garcia-Fons is currently touring along side the Italian clarinet/accordion duo of Gabriele Mirabassi and Luciano Biondini.

The Italians opened the show with an enthralling extended conversation on traditional folk-songs, middle-eastern themes (both are former members of Lebanese world-jazzer Rabih Abou-Khalil's band) and the odd jazz classic. Mirabassi's delicacy, subtlety of dynamics and shapely melodic development made a balletic contrast with the robust Biondini, who gave the accordion the staccato rhythmic force of percussion and reverberating low sonorities that sometimes suggested the St Barnabas church organist had joined in.

Mirabassi's clarinet vanished into sighs on an Italian first world war lament, danced euphorically on Abou-Khalil's Lebanese-Celtic-jazzy swinger Ma Muse M'Amuse, and nodded to the spiralling clarinet opener of Gershwin's Rhapsody in Blue on an exquisite account of Duke Ellington's Come Sunday.

Their melodic abundance challenged Garcia-Fons's greater dependence on riffs, world-jazz grooves and generally more familiar musical fallbacks. But you could have sworn the bass had become a viola on the player's opening passage, all his absorption of eastern and North African microtonal music, European classical music and jazz pouring out before a jig-like dance grew up around him.

Bruno Sansalone's bagpipes and eerily flute-like clarinet sound, and Antonio Ruiz's flamenco guitar were key elements. The latter complemented Garcia-Fons's childhood devotion to flamenco on a suite-like central section that developed through a driving pizzicato riff into an eruption of percussion.

But it was a slow rhapsody for desolate reed sounds and sustained high bass notes of aching tenderness that took the music to the level invited by Garcia-Fons's astonishingly imaginative virtuosity.

· At LSO St Luke's, London EC1, tonight (020-7638 8891) and South Hill Park, Bracknell, tomorrow (01344 484123).