'He commands light and shade’, wrote Busoni about Mozart, ‘but his light never blinds, and his darkness still shows clear outlines.’ If the two string quintets K515 and K516 – written at almost the same time – embody the two emotional extremes of the mature Mozartian universe, this new recording by the Quatuor Van Kuijk, plus the viola player Adrian La Marca, goes as far as any I’ve heard to demonstrate that miracle in action.

In other words, they repeatedly strike an incredibly fine emotional balance, and make it sound as if it’s the most natural thing in the world. There’s nothing precious or overwrought about these accounts: they’re buoyant, intelligent readings, vividly recorded with exactly the sense of a real, living chamber performance (intakes of breath; the occasional clatter of finger on wood) that so delighted David Threasher when he listened to the Van Kuijks’ recordings of Mozart’s ‘Haydn’ Quartets (12/19). Vibrato is used as an expressive device, and a sudden flash of sul ponticello lights up the Trio of K516: these players aren’t afraid to follow their fantasy, either.

Yet time and again, they seem to me to catch this music exactly where it speaks most powerfully: balanced perfectly – poignantly – between laughter and tears. There are shadows, as well as rough-cut humour, in the finale of K515; sweetness as well as taut, propulsive energy in the same work’s expansive first movement, and a restless sense of the music leaning forwards in the first movement of K516 – as well as an urgent, slightly anxious edge that throws the work’s sunny G major resolution into poignant relief. It all sounds so fresh, so warm, so unanimous – in short, so right.