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Percussion Keying Modification
The Hammond percussion effect is produced by borrowing the second or third harmonic signal from the corresponding manual drawbar, amplifying it, and returning part of the signal to the same drawbar. At the factory, the 1’ (9th) drawbar is used to key this effect, rendering that drawbar inactive when the percussion effect is switched on. A popular modification involves selecting another drawbar, typically the 1 3/5’ (7th) or 1 1/3’ (8th), to key the effect, thereby reactivating the 1’ for use with percussion. This is easily accomplished.
Looking into the back of the organ, locate the small 6 lug terminal strip attached to the manual chassis near the middle of the organ. Each lug has two wire attachment points. As you look in from the back of the organ, the lug on the far left has two white wires attached: the top wire goes to the percussion switch and the bottom to the 1’ drawbar. Complete these steps to change the percussion keying:
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