Their influences – shuffled in radically unfamiliar ways – include Romanian wedding songs, Schoenberg's serialism, baroque string techniques, free jazz and plenty of classical music, but the Transylvania-born pianist and composer Lucian Ban, and New York viola player Mat Maneri also leave a lot of room for the blues.

Ban and Maneri are touring Europe to promote the live ECM album, Transylvanian Concert. Ban opened this Vortex gig by barely stroking the soft opening chords of Not That Kind of Blues, while Maneri's deep, quivering viola tones drifted quietly in and out of the harmony – a microtonal player, he visits orthodox western pitches only in passing – before coalescing around a delicate blues theme. Ban began a rocking piano vamp that invited Maneri into swooping fast runs of sitar‑like plasticity and biting double-stop chords before the stealthy melody returned. The quiet beginnings of the ensuing piece swelled to a furore in which the two instruments almost indistinguishably fused. A standard song highlighted Maneri's bittersweet lyricism and Ban's affection for the support of pre-bop jazz pianists, notably Duke Ellington. As on the album, Maneri's tour de force was an unaccompanied reflection on the classic spiritual Nobody Knows the Trouble I've Seen – a ghostly murmur of low voices and skimming undertones. Ban followed with a mix of juddering chords and clanging runs that nodded towards Cecil Taylor's iconoclasm.

A second-half meditation on the late Paul Motian's Phantasm signalled the players' return to smoky delicacy, providing a highlight in a night that showed just how expressively rules could be broken and observed almost simultaneously.

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