Wilhelm Friedrich Ernst Bach was born on 23rd May 1759 and died on Christmas Day 1845. He was the son of Johann Christoph Friedrich Bach and the grandson of Johann Sebastian Bach. He received training in music from his father and from his uncle, Carl Philipp Emanuel Bach, and from another uncle in England, Johann Christian Bach. He held several musical posts during his life including Music Director to King Friedrich William II, Kapellmeister of Minden in 1786, and from 1788 to 1811 Kapellmeister in Berlin.
Das Dreyblatt for three players on one piano was written in such a way that it was to be performed with one large male in the middle and two petite females on either side of him. Wilhelm indicated that the man was to stretch his arms around the ladies to play the outside parts, while the ladies performed the middle parts.
There is no reason why these roles should be confined to the genders he suggested - though the middle (outer) player does need to have reasonably long arms.