Couplers are a special family of stops which interlink manuals (“inter-manual couplers”) or interlink notes on one manual (“intra-manual couplers”). Coupler stopkeys are, by convention, coloured black.
An example of an inter-manual coupler would be “Solo to Great”. By drawing this stop and playing on the Great, as well as the Great stops sounding, any Solo manual stops drawn will sound as well.
An example of an intra-manual coupler is the “Great Octave”. By drawing this stop and playing on the Great, for every note played, the note an octave above will sound as well as the note played. Sub-Octave couplers play the notes an octave lower as well as the notes being played. By way of example, these are the couplers available on a large 4-manual Wurlitzer organ:
Accompaniment to Pedal Great Octave to Pedal Solo to Pedal Solo to Accompaniment Solo to Accompaniment Second Touch Solo on Great Great on Orchestral Solo on Great Second Touch Solo on Great Pizzicato Intra manual couplers Accompaniment Octave Great Sub Octave Great Unison Off Great Octave Orchestral Sub Octave Orchestral Octave Solo Sub Octave Solo Unison Off Solo Octave
The Unison Off coupler silences the notes being played (sometimes to the confusion of the novice!) but – if the octave and/or sub-octave couplers are drawn – still allows these notes to sound.
Pizzicato couplers are a special form of inter-manual coupler that only allow the coupled manual to play for a very short moment, thus simulating the pizzicato of a string. Typically, a loud reed could be coupled to a softer flue registration to give a kind of ‘plucking’ effect. These were usually only found on large(r) Wurlitzer organs, e.g. Solo to Great Pizzicato.
Mutation couplers, which may function as inter- or intra- manual couplers, couple notes at pitches other than a pure octave (see link below).
See further: