As a form, the quartet develops within the framework of the gallant style and under the influence of entertainment towards the middle of the 18th century. It originates from the grouping of stringed instruments within the orchestra, leaving the double basses to double the cellos. Karl Stamitz and François-Joseph Gossec separate their quartets into two categories: those to be played with four instruments and those to be played by an orchestra... Luigi Boccherini (author of 91 quartets) was recently recognized as the father, together to Franz Joseph Haydn (author of 68 quartets), of the modern string quartet. From his first compositions of this genre we can see the skill of writing, the equal importance between the four voices and the decisive concerting role of the cello, an instrument of which he was a skilled virtuoso. In fact, the structure that later became "canonical" in four movements is not always respected in the corpus of Boccherini's quartets: many are in three movements, some (which he calls "quartets" for the printed edition) in two. This can probably be explained by the relative isolation in which Boccherini found himself operating for a good part of his life: Madrid in the second half of the eighteenth century was on the margins of Europe, musically speaking; this condition allowed him on the one hand to experiment in complete autonomy, on the other hand it did not offer him important quartet references with which to compare himself, at least until the last part of his life.