Haydn's chamber music centres on his 68 string quartets, a genre of which he was more nearly the literal ‘father’ than the symphony. Haydn’s six Sun Quartets Op. 20 concluded the astonishing series of eighteen works with which Haydn laid the foundations of the classical string quartet and was a decisive factor in the establishment of the composer’s fame. Together with the Quartets op. 17 composed during the previous year, the Quartets op. 20 operated on a level that no Haydn contemporary could even come close to matching, and it would not be exaggerating to rank this collection as one of the most manifold, most experimental, and most enthralling of the eighteenth century. Opp.9, 17 and 20 established the four-movement form with two outer fast movements, a slow movement and a minuet (although in this period the minuet usually precedes the slow movement). They also – op.20 in particular – established the larger dimensions, higher aesthetic pretensions and greater emotional range that were to characterize the genre from this point onwards. They are important exemplars of Haydn's Sturm und Drang manner.