Diapason

Long hours again this week, still working in Chesley every day. So far we have installed all the wind chests and wind lines, and most of the console, and completed all the wiring. The bourdon pipes—the largest—had to be set in place early, but all the rest, more than 300, remain to be installed, and that must be done tomorrow. Then begins the task of identifying and fixing dead notes (pipes that don't play when they're supposed to) and ciphers (pipes that play when they're not supposed to).

Here is the highest octave of the open diapason, the rank of pipes I spent Monday repairing in the shop. For 77 years the smallest ones had been tuned by mutilation, so they had to be reshaped and trimmed, then fitted with tuning slides. The open diapason produces the fundamental sound of the pipe organ, and is also called the principle stop.