Mozart complained that these three quartets – which may or may not have been commissioned by King Friedrich Wilhelm II of Prussia – were the product of ‘exhausting labour’. You’d never guess it from the music’s limpid melodies, gracefully shared between the four instruments, and deftly woven counterpoint. On the surface K575 and K589, especially, are the smoothest, most stress-free of Mozart’s mature chamber works. But as the Doric Quartet remind us, their largely untroubled euphony coexists with myriad textural subtleties. From the leisurely opening of K575, sotto voce as Mozart requests, the Doric are always responsive to the operatic impulse behind this music, phrasing the cantabile melodies with a vocal flexibility. Their collective tone is both sweet and sinewy, with vibrato used for expressive effect rather than as a default setting. Contrapuntal textures are ideally lucid; and the players’ natural give-and-take in Mozart’s instrumental dialogues bear out Goethe’s famous characterisation of the string quartet as ‘a conversation between four intelligent people’.

As in their ongoing Haydn series, the Doric take no phrase for granted. While the results are usually fresh and imaginative, there were moments when I craved more directness, more onward flow. At the opening of K590 – so different from the gracious symmetries of K575 and 589 – their tempo tweaks underline the quirky irregularity of Mozart’s phrasings and dynamics. Why not let the quirkiness speak for itself first time round and reserve playful and/or quizzical hesitations for the repeat? Similarly, in the magical contrapuntal passage at the heart of the first-movement development of K589 (from 3'37") the impetus slackens both the first time and, with minor differences, on the repeat as the players drift into reverie. It’s a beautiful effect once, perhaps, less so when heard twice.

These things are notoriously a matter of taste, of course. In any case, pleasure in the Doric’s performances far outran any misgivings. Each of the slow movements is eloquently shaped and coloured. The amorous exchanges in K575’s Andante evoke the world of the near-contemporary Così fan tutte; and with their easy two-in-a-bar flow, the players bring a serenading lightness to the 6/8 Andante of K590, plus a touch of scherzando skittishness in the recapitulation’s delicately pointed ‘Scotch snaps’. The minuets and finales, too, are inventively characterised. With its urgent tempo – a notch faster than in any recordings I know – and abrasive accents, the Minuet of K575 comes as something of a shock after the idyllic Andante. In the finale of K590 the Doric play up the contrasts between floating delicacy in the imitative counterpoints, fiery virtuosity and the rustic (by Mozart’s standards) closing theme (1'55"), its peasant drones duly pointed by the second violin.

The Doric are also properly intense in what for me is the most astonishing music in all these quartets, the Trio of K589. Twice as long as the demure Minuet, this does the opposite of what Classical trios are supposed to do, rising to a feverish climax, with virtuoso cross-string bowing for the first violin over a cello pedal. The Doric make this as exciting, and as unsettling, as I’ve ever heard. Recommendable rival versions of the ‘Prussian’ Quartets include the Alban Berg, 1975 vintage (Teldec, 9/76) – richer-toned and more straightforward than the Doric – and, on period instruments, the more intimate Mosaïques (Naïve, 5/99). With their questing imagination and colouristic range, the Doric are at least a match for both.