Following the loss of viola player Thomas Kakuska last summer, the Alban Berg Quartet has shown great resilience. It helps that Kakuska was able to anoint a successor, his pupil Isabel Charisius, during his illness; and it helps that while Charisius perhaps brings an extra spark of energy with her, she is clearly well attuned to her older colleagues.

In fact, in this programme of Mozart and Bartok if it seemed that something was missing from the quartet's performance, it perhaps involved the first violin part rather than any other. The two Mozart works played - the Quartet in G major, K387, and the Dissonance Quartet, K465 - have passages that require concerto-soloist brilliance from the leader, and Günter Pichler wasn't quite enough the showman. Rather than drawing us in with imaginative or consciously eloquent phrasing, he often seemed content to concentrate on the larger-scale shape of each movement, holding the listener at arm's length.

They remained satisfying performances, and the Dissonance Quartet brought the odd moment of held-breath poise. The intensity of its slow movement - one of Mozart's most beautiful in any genre - was captured in playing of considerable emotional range.

However, the rawer edges of Bartok's Quartet No 2 seemed to unleash Pichler's expressive potential as, at the start, he spun out his weird lullaby over the rocking second violin and viola. Individual instruments emerged from, and were reabsorbed into, a finely balanced blend. The second movement was a roller-coaster ride of charged aggression and, in terms of the constantly fluctuating tempos, remarkable polish; the dramatic chords of the third movement, burgeoning from silence, had even more impact.

The encore, too, was of Bartok - the slow movement of his Fifth Quartet, dedicated to Kakuska's memory. Despite the warmth of Charisius's playing at the heart of the ensemble, it spoke viscerally of absence and loss.