20th-century term for an organ in which the principle of ‘extension’ (making one row of pipes available at different octave or overtone pitches) is applied to a major degree. Praetorius (Syntagma musicum, ii, 1618, 2/1619/R) drew a table-positive in which the chest of a single row of pipes was so grooved and palletted that it could supply each key with three tones (2', 1 1/3' and 1'); a few larger examples are known to have been made over the next two centuries or so, but clearly the non-mechanical actions of the late 19th century gave greater opportunities for the system, since they made it easier for key-action and chest-construction to be designed for this purpose. Audsley (The Art of Organ Building, 1905) used the terms ‘borrowing’ for a rank extended beyond the keyboard compass in order to make it available at another octave (e.g. 116 pipes could provide stops at 32', 16', 8', 4', 2' and 1', each to a compass of 56 notes) and ‘duplicating’ for using a rank of pipes on two or more keyboards, manual or pedal, called ‘communication’ by English builders from about 1650 to 1800. Marcussen’s organ at Siseby (Schleswig, 1819) used both systems; the electric ‘unit organ’ of 1930 took it a step further by giving each pipe its own action playable by any key desired. The principle is quite different from that of the Coupler, which unites whole keyboards.
See Organ, §VI, 4.
PETER WILLIAMS