Glasgow Jazz Festival 2013's main core of concerts doesn't begin until Wednesday but this "one week from now" overture could hardly have been bettered as an appetiser.

Saxophonist Konrad Wiszniewski and pianist Euan Stevenson's New Focus has developed a life and identity of its own since its premiere at Edinburgh Jazz Festival in 2011. It's been praised from here to London and back. Its recorded version was longlisted for the Scottish Album of the Year award and, possibly most pleasing of all, on the evidence of the new material played here, it's moving into an equally attractive-sounding, potentially even more rewarding new phase.

The basic triumph of the project has been well rehearsed but stands being repeated: a jazz quartet working with a string quartet and concert harp in compositions and arrangements that bring these apparently diverse elements together into a natural, flowing music. The way Wiszniewski's tenor merges with the strings is at times heart-breakingly gorgeous, and while Stevenson's phrasing on solos is the essence of cool, the heat that the nonet can generate degree by degree, with the expert shovelling on of coal from Alyn "Fireman" Cosker on drums, is truly exhilarating.

A brand new – finished that morning – ballad for cello, piano and tenor confirmed Stevenson's master-of-his-materials composing credentials, with superb melody sharing between the three players, and the waltzing The Simple Life, for all nine instruments, danced its way into the repertoire with gracefulness, an easy swinging pulse and an improvising bite from Wiszniewksi that, like the music as a whole, hit home with a huge sense of satisfaction.

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