Köthen period (BWV 1007–1010); probably Leipzig period (BWV 1011 and 1012 → style, instrument) planned as a 2nd part for the violin soli (BWV 1001–1006); earliest manuscript copy around 1727–1731. In addition to the explicit mention of a violoncello in Anna Magdalena Bach´s copy, an instrument which was not standardised in size, design and style of playing at the time, the execution on other Instruments like violoncello piccolo, viola, viola da spalla etc (all used by Bach in multiple works) is also possible. The Leipzig-based Instrument maker Johann Christian Hoffmann built (at the instigation of Bach) a 5-stringed Viola pomposa, which was held on the arm, such as BWV 1012 requires. Bach arranged BWV 1011 for lute at a later time, see BWV 995.
