If ever a Mozart recording were self-recommending, this is it. The first four volumes of the French-Russian duo’s complete sonata cycle came close to my Mozartian ideal. This final instalment, again juxtaposing early, middle and late works, fulfils every expectation. They play the two fragile early sonatas, composed when the wunderkind was barely out of nappies, with charm, simplicity (no over-sophisticated inflections) and – say, in K11’s chuckling contredanse finale – an impish sense of fun; and while Tiberghien inevitably leads the show here, Ibragimova judges to a nicety her little interpolations and echoes. With their seemingly instinctive mutual understanding, the players constantly ensure that there is no whiff of routine in these ingenuous childhood works.

Even Tiberghien and Ibragimova cannot quite convince me of the stylistically dubious posthumous arrangement of the late B flat Piano Sonata, K570. In the Adagio and finale, especially, the added violin figuration compromises the music’s lean, rarefied grace. The little-known set of variations on a popular French chanson, K359, can seem slight on the page. But, true to form, Tiberghien and Ibragimova bring the music tinglingly alive, with new timings and subtle changes of tone colour and emphasis on repeats. Mozart, a born show-off, would surely have relished the swashbuckling flamboyance Tiberghien brings to the pianistically brilliant Variations 6 and 10.

As to the mature sonatas – each of them a true democracy – it’s hard to imagine more delightful or discerning performances. Ibragimova, with her astonishingly varied tonal palette, and Tiberghien combine the wisdom of long experience with a spontaneous joy in music that is so often opera buffa by other means. Crucially, both players understand the essentially vocal nature of Mozart’s inspiration. If you don’t smile at the quickfire banter in K526’s opening Allegro, amid ever-unpredictable phrasing and shading, you haven’t been listening. Grace, wit and delicacy coexist with a quasi-orchestral grandeur and boldness in the opening Allegro of K380 while the Presto finale of K526 emerges, rightly, as a coruscating double concerto without orchestra, each player vying with the other in virtuosity. Most memorable of all are the slow movements: the wistful G minor Andante con moto of K380, and the Andante of K526, music at once austere and visionary. Keeping each movement flowing, Tiberghien and Ibragimova distil a quality of rapt inwardness, not least in the quietly shocking harmonic progression that leads back to the main theme in K526.

Occasionally in these works – say, at the fermata in the gentle ‘walking’ finale of K302 (at 4'19") – the players resist Mozart’s invitation for a brief improvised cadenza or a touch of added ornamentation. But, on disc at least, better too little than too much. The recorded balance, as in previous issues, is spot-on, and Misha Donat’s detailed notes, going far beyond the obvious, are doubly welcome given that Mozart’s violin sonatas are among the least written-about areas of his output. ‘A set that will surely become the modern reference recording’ wrote David Threasher after Vol 4, a claim I would enthusiastically endorse after this superlative final volume.