Hindemith is the viola composer par excellence for the 20th century but others took up the mantle, not least in Hungary. Bartók’s Concerto may be the most familiar (and its completer, Tibor Serly, also wrote one) but Ligeti’s unaccompanied Sonata (1991-94) has become one of the viola repertoire’s key enhancements. In six contrasted movements, this work has become to the viola what Bartók’s 1944 Sonata is to the violin, reflected in at least seven recordings.

The opening ‘Hora lunga˘’ (Slow song) is played on a single string – the C – and enchants with its folksong-like melody. As usual with Ligeti, nothing is what it seems: the melody is artificial, the folksy atmosphere soon disrupted by microtonal incursions. That first movement and the concluding ‘Chaconne chromatique’ were written for Tabea Zimmermann, whose 1997 recording remains the benchmark for all rivals, but Kashkashian is just as convincing, her tempi more measured than Knox (at under 20 minutes, too swift), Power and Tamestit, her tone far more grateful to hear than Strosser. The remaining four movements mix fiery pyrotechnics and emotionally complex memorials of which Kashkashian is a fine interpreter.

She is even more on her mettle in György Kurtág’s 19-movement collection Jelek, játékok és üzenetek (‘Signs, Games and Messages’), started in 1989 (using some pieces begun even earlier) and still being added to, though since 2001 only revisions have been made, no new pieces. The movements range in span from three or four minutes to handfuls of seconds. Each piece is beautifully crafted but collectively may be too much of a good thing, even in such a superb rendition. A disc for specialists, perhaps, but a special one.