Coupler

(Fr. accouplement, tirasse; Ger. Koppel, Koppelung).

The mechanism in an organ or harpsichord whereby pipes or strings of one department or manual are made to sound an octave lower or higher, or on the keys of another manual. The most common system until the early 19th century was the Schiebekoppel or shove coupler: one set of keys was pushed in or pulled out to enable some kind of wooden protuberance along the key-shafts (dogs, lugs, small vertical battens, etc.) to connect in one way or another with a second set of keys and so cause them to be depressed likewise. Usually a coupler could not be engaged while playing since both hands were required to move the keyboard by grasping blocks at each end and since (even if the motion to engage the coupler is controlled by a pedal or knee lever, as in some late 18th-century French harpsichords) the coupler dog on a key being played would, if one attempted to move it into the coupling position, block against the side of the point of contact of the key of the second manual. During the early 19th century other more easily manipulated mechanisms came into common use: (a) the function of the protuberances attached to the keys was taken over by sets of stickers or other pieces held by a movable batten that was connected to a stop knob or pedal, or (b) connections were made between the internal elements of one division’s action with those of a second division (thus in most cases not moving the actual keys of the coupled division). Octave couplers, requiring a set of diagonal backfalls to connect a key or its action with the key or action an octave lower or higher, appeared in Italy by the 18th century, where they were called terzo mano (‘third hand’). They became relatively common throughout Europe during the 19th century.

In organs, couplers were probably known in the 15th century. At the Oude Kerk, Delft, in 1458, it was specified that the Chair organ might be joined to the Great organ when the organist desired. Henri Arnaut de Zwolle (c1440) described a coupler based on lugs that could be brought into play. Pedal-to-manual couplers were probably also made at the same period, but as in the case of other accessories like Tremulants, builders’ contracts did not always specify couplers. From the 16th century onwards, especially in organs without separate pedal pipes or with only one or two ranks of low-pitch pipes, pedals were often permanently coupled to manuals, usually to the main keyboard (Great organ). This was accomplished by linking the pedals to the manual keys or action via a pull-down system (Ger. angehängtes Pedal) or by providing the manual wind-chest with a second set of pallets controlled by the pedal keys (Ger. Ventilkoppel, Windkoppel). The latter system is found in the organ by Jörg Ebert in the Hofkirche, Innsbruck (1555–61) and in most of Gottfried Silbermann’s smaller instruments. A further system known as the transmission or communication system also apparently existed by the 16th century; this was a more complex arrangement of doubled pallets, grooves and sliders which allowed individual stops to be coupled from one division to another, often from manual to pedal but also from manual to manual. Before 1820 the permanent coupling of manuals to pedals, via pull-downs, was quite widespread in English organs, but manual couplers were less common. Swell to Great and Octave couplers emerged during the 1820s and 30s, and a sforzando coupler pedal was provided by H.C. Lincoln at St Olave’s, Southwark, in 1844. Sub- and super-octave couplers featured in organs displayed in London at the Great Exhibition of 1851 and the rise of pneumatic and electric actions allowed the development of various new coupler mechanisms, including those that enable a rank of pipes to be played at various different pitches in the so-called Extension organ. In organ music, coupled manuals are often implied by the terms organo pleno, grand jeu or grand choeur.

In string keyboard instruments, the earliest known couplers are in late 16th-century Flemish ‘mother-and-child’ virginals (‘double virginals’), in which the smaller instrument at octave pitch can be placed on top of the larger one at unison pitch, in such a way that the latter’s jacks act as coupler dogs to move the small instrument’s keys. The earliest known couplers in harpsichords are shove couplers in French two-manual instruments made in the mid-17th century. The shove coupler remained a standard feature in French harpsichords and was also made in Germany. The Dogleg jack served as a coupler in some German instruments and seems to have been the only sort of coupler made by English and Dutch harpsichord builders. A remarkable oddity is the octave coupler in a single-manual harpsichord by Giuseppe Maria Goccini (1725; now in the Tagliavini Collection, Bologna), in which the keys from G to f are coupled to the lower octave, while the keys from c' to c'' are coupled to the upper octave.

PETER WILLIAMS/JOHN KOSTER, CHRISTOPHER KENT