The rough preliminary designs, and the isometric drawing (Adam volumes 52/7, 6/127, 25/9) show different designs to the others.

The finished and record drawings are colour-washed and suggest the use of painted ornament on the harpsichord case. The instrument illustrated in the Works in Architecture of Robert and James Adam, however, is said to be inlaid with coloured woods.

None of these designs were brought to fruition, although an instrument decorated to a much altered scheme was executed, and survives in the boudoir of Maria Feodorovna, Grand Duke Paul's second wife, at the Palace of Pavlovsk (see scheme notes).