The Transposing Keyboard
by Hendrik Broekman
Evidence for establishing pitch standards of the 18th century indicates that there was no single standard but that most musical performance in the baroque era took place at pitches lower than A-440 Hz.
Surviving harpsichords are one source from which evidence can be adduced. When we mount wire analogous to that used by the ancients on our close copies and pull it up only to find that it will break before it reaches modern pitch, we must think twice about what pitch we will use as a standard. Another result of pitching a keyboard instrument at A-440 Hz is a slight penalty in the structural longevity of the case due to excess stress (12%) imposed by the elevated pitch. Most importantly, we now realize that instruments sound richer and more sonorous when strung with lower tensile wire similar to that used by 18th century builders, and when pitched at A-415 Hz or A-392 Hz, one half tone or one whole tone below A-440 Hz.
The Transposing Keyboard provides a satisfactory compromise suited to 20th century pitch standards, the modernized instruments with which the harpsichord must play, as well as the more severe physical environments which all centrally heated buildings impose. Transposition is accomplished by the simple device of sliding the keyboard sideways to operate a different selection of jacks. This permits the instrument to play at different pitches without the need for retuning every string.
Today most Hubbard custom built instruments and all Hubbard kits are designed to be used at A-415 Hz. Transposing keyboards are provided to accommodate use at modern pitch. Older Hubbard custom instruments can be retrofitted for the Transposing Keyboard. The cost is US$500. Hubbard kit builders interested in converting their instruments to transposers (single or double) are encouraged to write for instructions and parts. Parts required total US$125 for the single-manual kit and US$150 for the double-manual kit. Instruments from the mid-70's with front guided keyboards will require special instructions.
For those players and technicians confronted with the Transposing Keyboard but unfamiliar with its use, the procedure listed below should be followed:
All stops should be turned on so that the dampers help support the jacks as the key ends pass beneath them. With the manuals coupled, play each note in turn to insure that the jacks are supported by the dampers. The transposing shim should be tipped up and pulled out. Supporting the lower end blocks with fingers (especially thumbs) and being sure that the end keys are not depressed, slide the keyboards slowly to their new position. Do not force. If the keyboards resist, a jack is caught somewhere, usually in the lowest or topmost set. This requires that the jack rail be taken off and the jack freed by lifting it up. Replace the transposing shim in the other side. The instrument should be tuned to A-415 in low position. It should be transported with the action in low position (i.e., with the transposing shim at the treble end).
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. updated: 11/13/03