Six works belong to opus 9 – the first group of Haydn's string quartets of which we know. The composer also went new ways as far as form was concerned: whereas he had still adhered to the five movement divertimento in the previous quartets opus 1 and 2, in this case he favored four movements, something he continued in the future. Apart from this, he also expanded the register and experimented with metric surprises (for instance in the trio of the minuet from the G major quartet). This study edition, introduced with a preface by the Haydn specialist Georg Feder, complements our proven parts edition HN 206 and now presents these popular works to all music lovers in score form.