Franz Josef Haydn (1732-1809) composed his String Quartets (6) published as his Op. 20 in 1772. Although the published edition places the String Quartet in D major for two violins, viola and cello, H. 3/34, as fourth, from the internal evidence it seems likely that the String Quartet D major was in fact composed last. Part of the reason is the naming of the parts in the autograph (the cello part is marked Violoncello and not Basso). Part of the reason is the order of the movement (with the Menuetto third as in most of Haydn's later quartets and not second as in his early quartets). Part of the reason is the words Haydn chose to write at the end of the score ("Gloria in Excelsis Deo," connoting gratitude, and not his standard "Fine Laus Deo," connoting completion).
But the largest part of the reason is the forward-looking nature of the music. The opening Allegro di molto in triple time is built of motives and not melodies and each motive is developed in a tightly controlled and entirely compelling manner. The following Un poco adagio e affetuoso in duple time and the tonic minor is a deeply affecting set of variations upon an 18-bar original theme with three variations, a reprise, and a fantastic coda of 32 bars. The following Menuetto is a form of concert gypsy music with the theme presumably taken from a gypsy original. The closing Finale marked Presto e scherzando in common time is even more markedly gypsy-like in origins and effect. Haydn handles the mixtures of styles and moods seamlessly, a brilliant example of his ability to create unity even in the diversity that marked his later music.