It's hard to imagine a work less suited to string quartet than Bach's Art of Fugue, and yet the Emerson String Quartet braved this vast contrapuntal edifice in their latest Wigmore Hall concert. Bach left no instructions for how the piece should be played, and the whole work is both an abstract, virtuosic display of polyphony, and an open-ended kit for performance.

The Emersons performed a 50-minute selection from the piece, charting a labyrinthine musical journey from the first fugue, Contrapunctus 1, to the vast, unfinished fugue at the end of the piece, the last music that Bach ever wrote. A single, humble theme was the Ariadne's thread that connected virtually every piece, from the gigue-like brilliance of the second fugue in the Emerson's sequence, to the rigorous austerity of a chromatic fugue for three of the players.

There was more to the Emerson's playing than cerebral contemplation, and they created a journey that was as expressively satisfying as it was contrapuntally compelling. They turned the faster fugues into dynamic dances, while the slower numbers were models of structural reflection. Yet the end of the performance was enigmatic, as the huge final fugue suddenly froze into silence, the Emersons finishing in mid-phrase with the last notes that Bach composed.

It was a prescient preparation for the Emerson's second half, and their performance of Beethoven's late C sharp minor String Quartet, which began with another mysterious fugue, almost as if Beethoven were contributing to his own Art of Fugue. The Emersons revealed the extremity of this quartet, with its seven-movement structure that veered from the radiance of the slow movement to the irrepressible violence of the finale.