The Goldberg Variations are a pinnacle of Bach's art. Conceived for harpsichord, the work has been transcribed for quite different instruments, including string trio, guitar, synthesiser and harp. Richard Boothby's version for his own consort of viols, Fretwork, is arguably the most unusual, in that it opts for a soundworld that looks even further back in time.

Part of the justification for such a setting must be Bach's own liking for viole da gamba, already then old-fashioned. Even so, hearing the treble viol intone the opening Aria – the theme on which the 30 subsequent variations are based – came as a shock, with its gentle intimacy given an almost ghostly effect. Boothby's setting is dexterously divided between various combinations of the treble, tenor and bass viols, and he achieved some magical effects, notably in variation 20, when a single tenor was accompanied by pizzicato bass viols, and in variations of gossamer passagework.

But the virtuosity demanded by these variations is unrelenting. Though it was evident that Boothby's involvement in the transcription has imprinted every note on his consciousness, there were some, let's just say fretful, moments when the necessary precision eluded the players. Happily, those moments were ultimately rendered negligible by the cumulative force of the later variations, crowned by the humorous Quodlibet, where Bach, just for fun, throws in a number of jaunty folk tunes. The final return to the opening theme, bringing the piece full circle, took on an almost ascetic purity.