Our Either/Or registration system
What is Either/Or?
Either/Or Registration is a system whereby stops can be registered on either one manual or the other. Not to be confused with "duplexing" or "borrowing," commonly found in electric action organs, Either/Or utilizes a slider chest and is fully compatible with the finest mechanical action. Many smaller Bigelow organs use this system.
Advantages of Either/Or
In a small tracker organ, Either/Or has two distinct advantages:
1) It allows for more complete choruses
2) It greatly enhances flexibility in registration.
History of the Bigelow Either/Or System
The development of Bigelow's Either/Or system began with Opus 1, which has twelve Stops. The flutes and higher pitched principals including mutations are playable on Manual II by drawing the stop knob half-way out.
Opus 6 and 7 expanded the Either/Or concept by making all stops except the Praestant 8 available on either manual. Adding pedal channels to the manual chest allowed transmission of the Praestant 8 and the Trumpet 8 to the Pedal.
Beginning with Opus 8, stop knobs moved from side to side, instead of in and out, and the center position was Off. This solved the problem of momentary "blurbing" if stops were added to or retired from Manual I while playing on Manual II.
Opus 16 further expanded the Either/Or concept to include pedal stops. It contains the largest number of Either/Or stops of any Bigelow organ to date. The Quintadena 16 and Praestant 8 are shared between Manual I and Pedal, and the Dulcian 16 is available on Manual II or Pedal.
Beginning with Opus 19, the sliding stop knobs move vertically instead of horizontally. This was felt to be more intuitive for the organist: Move the stop up for the upper manual, down for the lower manual. The pedal divisions of Opus 19 and Opus 23 each include an octave coupler and a unison off, making eight-foot tone available in the pedal independent of the manuals.
With Opus 25, sliding stop knobs were abandoned in favor of pairs of mutually canceling conventional draw knobs. This has proven to be the most user-friendly system. Building on this, Opus 26 includes a solid-state combination action, making it the world's first Either/Or organ with dual registration, as far as we know.
How does Either/Or work?
The heart of the Bigelow's Either/Or system is a slider chest containing tone channels for two manuals. The channels are arranged with the corresponding notes of each manual next to each other. (For example: C of Manual I, C of Manual II, D of Manual I, D of Manual II, and so on).
A single slider is bored in two positions, once into the Manual I channels and again into the Manual II channels. Borings are arranged so that when the Manual I holes are open the Manual II holes are closed, and vice versa. There is also a position in which all holes are closed. The Manual I boring and Manual II boring for a given note are channeled together in the toeboard. In this way, a given pipe may speak from either one of two sources. The stop knob or lever connected to the slider has three positions: Manual I, Manual II, and Off.
Alternatively, and more recently (see History, above), a separate slider is used for each manual. A conventional (i.e.: on or off) draw knob, one for each manual, is connected to each slider, and they are inter-connected so that drawing one stop cancels the other and vice versa.