The most remarkable, unexpected, and surprising of the works that came to light in Köthen, where Bach worked from December 1717 to April 1723, are those for violin and cello that Johann Sebastian conceived without the support of any accompaniment, entrusted to either a figured bass or to a cymbal playing in alternating ‘concertante’ manner.
The two collections – each comprising six compositions arranged to an overall scheme presumably with the view to a printed edition – differ both in content and form, but are in some ways complementary. The first collection to be compiled was probably the one with the works for unaccompanied violin, as would be attested by Baßo | accompagnato. | Libro Primo. | da | Joh: Seb: Bach. | ao. 1720. The work (which has come down to us in six other copies made by different hands, one by Anna Magdalena Bach) includes three sonatas and three suites (BWV 1001-1006). The alternating succession of sonatas and suites (the latter made up of a series of dances, in one case preceded by a prelude) should not however be seen as a succession of six entirely autonomous and independent musical entities (even if Bach speaks of Sei Solo, typical of the editorial custom of the age), but rather as the presentation of three couples of compositions of which the second term or member of the couple is the continuation or corollary of the first; in other words, what we have is integral sonatas, a suite of dances as it were, following a tradition that was by no means rare for the music of the time.