angeblich....
https://www.bach-cantatas.com/Lib/Trebs-Heinrich.htm
"However, H.N. Trebs’ greatest claim to fame is his rebuild of the Weimar palace chapel organ (Ludwig Compernius, c1758) at the instruction of J.S. Bach himself. A contract for the alterations was signed on June 29, 1712. Of this rebuild little is known, except that eith J.S. Bach or the Duke of Weimar has determinded that the instrument should include Glockenspiel, and that great trouble was taken over obtaining bells from dillers in Nürnberg and Leipzig. Trebs’ work was playable by the middle of 1714 (2/24), having completed two weeks of tuning by May and received final payment in September."
Ähnlich wird es dargestellt in Christoph Wolff Biographie Johann Sebastian Bach, The learned Musician. Dort steht dass Bach die Pläne entworfen habe, auch für die Renovierung der Orgel in Mühlhausen.