The new album from Swiss piano trio Vein springs a couple of double takes with its cheesy election-poster cover and bursts of Fats Walleresque old-school swing. But on their short UK visit with US saxophonist Greg Osby, their casually borne scholarship, improv edge and ingenious themes steered an intently focused show. The London jazz festival is reportedly considering a Swiss thread this autumn, and – as one of Europe's most exciting ensembles – Vein would seem a racing cert for it. But at the Vortex, the dynamic and virtuosic Osby's guest presence was unquestionably a huge plus.

Pianist Michael Arbenz's jaggedly snappy Under Construction opened the gig, and his brother Florian's cymbal smacks and bristling snare-patterns delivered its curt accents in harness with Osby's piercing alto sax. Both Arbenz brothers and bassist Thomas Lahns have broad classical as well as jazz experience, and a compositional approach was evident when the opener's spikiness quickly gave way to a graceful, full-toned bass solo and hushed piano variations, before Osby's return with a torrent of fierce postbop.

The saxophonist's Dialectical Interchange was a contrasting tale of pure, faintly mournful tones at first, but grew choppier with the arrival of a band-groove. A billowing Lahns bass solo introduced a medley of three trio tunes, and a showcase for the Arbenz brothers' empathy that passed through a hurtling percussion improvisation under clanging piano chords, and wound up as a Bill Evans-like romantic jazz ballad. A fast swing beat brought Osby back with a solo that began Wayne Shorter-like feints and rhythm tweaks, but stretched out into seamless runs that grew longer and longer, and an eruption into free-jazz showed they all find shapely stories in that mode too. Vein might risk being almost too smart and knowing for the more ascetic of raw-food improv fans, but almost everyone else won't mind a bit.