King Arthur is one of Henry Purcell's semi-operas – a Restoration drama blending text by John Dryden with music, dance and often outlandish stagecraft. The full work tells of Arthur and the Britons battling against Oswald's heathen Saxons, its timely patriotic subtext promoting a happily unified Britain. But as the protagonists (including Arthur and Oswald) are spoken roles and Purcell's songs are left for supernatural spirits, sirens and peasants, most of what we get in a concert performance that ditches the text – as this one did – revolves around seduction and drunken masques.

The numbers from all five acts fit neatly into a two-hour concert and sounded stylish, if underwhelming, here from Harry Christophers and the Sixteen. The 30-strong period instrument band phrased the pieces beautifully and buoyantly but were a little anaemic in tone, needing beefier bass in the Usher Hall. The choruses were full bodied and balanced; members of the Sixteen also took solo passages, some with better results than others.

Best by far of the named soloists was soprano Sophie Bevan. Her delivery is refreshingly unfussy and her voice voluptuous and grainy, which complemented the Sixteen's silvery violins perfectly in The Fairest Isle. Tenor Robert Murray sounded more cautious and couldn't match Bevan's decibels, but he shone with a lilting How Blest are Shepherds. Bass-baritone Jonathan Best was a last-minute stand-in and struggled to bring his arias to life: the Frost Scene, where dry-clattering violins and shivering voices evoke a frozen landscape, was disappointingly dull. But mostly Christophers drove the whole thing with easy grace. He doesn't seem to micromanage his musicians, at least not in concert, which makes for an engaging sense of ownership from everyone on stage.