Identified through on-line information from James R. Stettner. -- In 1845, the organ was removed by the Hooks to their shop in Boston for repairs and to add a pedalboard and Sub Bass register. This would have been an open wood set of pipes. A 12-note chest and pipes were built and installed at the rear of the organ. That chest was retained and reworked in the 1893 rebuild by George Peirce. No other tonal or structural changes are known to have been made at the time of this work. Source: Bob Newton, Andover Organ Co.