Even by the high standards of the Machynlleth festival, the richly resonant sound of the Leopold String Trio seemed to take its audience by surprise. But then this is an ensemble who have effectively redefined both medium and repertoire, scotching any lingering perception that they might be deficient in the violin category. With regards to the programme, the combination of Boccherini, Taneyev and Alwyn is certainly not a common one, yet the Leopold players made each piece an exploration in texture and timbre that was absolutely compelling. In Boccherini's Trio in D, Op 14 No 4, they conveyed a depth of feeling in the minor mode Andantino that suggested the composer was far more that a purveyor of pretty galanterie. And the wit of defied expectations in the finale's numerous false endings was sustained to the last.

Tchaikovsky hailed his friend Taneyev as a master of counterpoint. It was Taneyev's obsession with organising the contrapuntal voicing of his material long before he wrote out his pieces that permitted musicologists to complete his Trio in B minor; its two movements were left only in sketch form at his death. The Leopold gave it a blistering performance here, reflecting Taneyev's passion every bit as much as the craftsmanship. Similarly, the trio by William Alwyn, dating from 1962, was played with a vibrant intensity, respecting the formal rigour underpinning the four-movement structure but also finding a deeply emotional core. Nowhere was this more potent than in the Cavatina, where the anguished ardour of the climax was wonderfully realised by violinist Isabelle van Keulen.

It is precisely the capacity of each individual to match the others in depth of tone and expression that makes the Leopold so special. The instinctive way they homed in on the moments of incipient genius in Beethoven's Trio in E flat, Op 3, was further testimony to their profound corporate musicianship.