‘They are full of invention, fire, good taste and new effects,’ wrote Charles Burney upon hearing Haydn’s Op 76 Quartets in London, ‘and seem the product, not of a sublime genius who has written so much and so well already, but one of highly cultivated talents, who had expended none of his fire before.’

They listened to string quartets in 18th-century London in a different way to the Viennese. The emergence of an affluent mercantile class in the English capital had given rise to well-attended public concerts, whereas at home in imperial Austria chamber music was the province of the monied and titled upper classes. Haydn returned to Vienna with a new realisation of how such intimate forms could operate on an almost symphonic canvas for the entertainment of a large room filled with a paying audience, rather than remaining the property of a prince, count or baron, performed in his private salon and shared only with his closest family or friends. Haydn’s first response to this newly ignited awareness was the set of six quartets, Opp 71 and 74 (1793), dedicated to Count Anton Georg Apponyi, scion of an ancient Hungarian noble family, but clearly conceived for the violin virtuosity of Haydn’s London impresario Johann Peter Salomon, who gave their first performances there before a large and potentially noisy crowd. A few years later, now back permanently in Vienna, along came Op 76, once again dedicated to a senior minister in the Habsburg civil service, one Count Joseph Erdödy, though planned on a still grander scale for the broadest possible public.

Since the ‘Sun’ Quartets, Op 20, in 1772, Haydn had periodically produced further sets of three or six in which not only was his mastery of the form complete, but each work was imbued with its own individual character. Op 76 was composed in 1796 97, when Haydn was in his mid-sixties, and stands as the finest quartet set of the century. In these six works, Haydn pushes the possibilities of the form further than ever before. Musical arguments are wound tauter; contrasts between learned counterpoint and popular folk styles are starker, more sudden, more unpredictable, more eccentric; the architecture is on the most expansive scale, the gestures unmatched in their boldness. Slow movements are more profound than ever, minuets (many of them scherzos in all but name) more impish. And once again, although the six works fit together perfectly as a set, each is sharply characterised to contrast with and complement the other five.

The second half of the set (as numbered) outdoes even Nos 1 3 in making a mockery of the quartet conventions Haydn himself had done so much to establish. In Nos 5 and 6, Haydn even abandons the traditional sonata form for his opening allegros, shifting the expressive weight in each work to the slow second movement. It is in these – harmonically adventurous, formally ambiguous – that the London Haydn Quartet are often at their best, distilling an atmosphere of striking intensity in the ecstatic F sharp major Cantabile e mesto of No 5 and the resonant depths of the B major ish Fantasia of No 6.

The opening of the Sunrise (No 4) is similarly rich, leader Catherine Manson taking her time and unfurling the movement’s thematic material with improvisatory freedom. Alina Ibragimova with the Chiaroscuro Quartet is just as rhythmically spontaneous here; although as the movement progresses and the rhythm becomes more regular, the Chiaroscuro score in pushing through where the LHQ place a minute stress on each down-beat, which then holds back the music just when it should gallop free. You feel the same effect at the opening of No 1, whose cheeky theme is exposed winningly by the LHQ’s four players upwards from cello to leader, before the same foursquare phrasing, at a rather careful tempo, prevents the music from slipping the leash and dancing off, unshackled from all inhibitions.

This is often the case: where the Chiaroscuro fully acknowledge the animation and ebullience of the faster music, the LHQ seem to recognise the allegro injunction but not the qualifying con spirito of the first movements of Nos 1 and 4, or the spiritoso of the finale of No 6. In this latter, the Chiaroscuro revel in the anarchy of Haydn’s rhythmic games, while the LHQ clearly feel they should play nicely together, in the process adding three quarters of a minute to the playing time.

In that respect the LHQ set is clearly of a piece with previous instalments in their cycle: as Richard Bratby remarked on their Opp 71 and 74, ‘these are thoughtful rather than playful performances’, missing ‘a sense of playing to an audience, of creative exaggeration, of theatricality’ (A/19). Listen to the finale of No 5 or the presto Minuet of No 6 in the Chiaroscuro’s performance for armfuls of just that playfulness and theatricality. Comparing these two period-instrument sets demonstrates once again that there is no single (or ‘right’) way to approach the infinitudes contained herein. The LHQ enjoy the more generous sound stage but it is the Chiaroscuro Quartet who lap up most voraciously the invention, fire and effects of these miraculous works.