A Dictionary of Music and Musicians/Swell-Organ
SWELL-ORGAN. The clavier or manual of an organ which acts upon pipes enclosed in a box, such box having shutters, by the opening of which, by means of a pedal, a crescendo is produced. The shutters are made to fold over each other like the woodwork of a venetian blind, hence the expressions 'Venetian Swell' and 'Venetian Shutters' sometimes found in specifications. To the swell-organ a larger number of reed-stops is assigned than to other manuals. [App. p.797 "The sentence in lines 5–8 of article is to be corrected, as the Venetian Swell was not named from the Venetian blind, but the Venetian blind so called because it was worked on the same principle as the harpsichord swell."]
The first attempt at a 'swelling organ' was made by Jordan in 1712. The crescendo was obtained by raising one large sliding shutter which formed the front of the box. The early swell-organs were of very limited compass, sometimes only from middle C upwards, but more generally taken a fourth lower, namely, to fiddle G. For many years the compass did not extend below Tenor C, and even now attempts are sometimes made to reduce the cost of an organ by limiting the downward compass of the Swell; but in all instruments with any pretension to completeness the Swell manual is made to CC, coextensive with the Great and Choir. [See Organ, vol. ii. p. 596, etc.; also 604.][ J. S. ]