Enclosure and Expression Pedals
On most organs, at least one division will be enclosed. On a two-manual (Great and Swell) organ, this will be the Swell division (from whence the name comes); on larger organs often part, or all of, the Choir and Solo divisions will be enclosed as well.
Enclosure is the term for the device that allows volume control (crescendo and diminuendo) for a manual without the addition or subtraction of stops. All the pipes for the division are surrounded by a box-like structure (often simply called the swell box). One side of the box, usually that facing the console or the listener, will be constructed from horizontal palettes (wooden flaps) which can be opened or closed from the console. This works in a similar fashion to a Venetian blind. When the box is 'open' it allows more sound to be heard than if it were 'closed'.
The most common form of controlling the level of sound released from the enclosed box is by the use of a Balanced expression pedal. This is usually placed above the centre of the pedalboard, rotating away from the organist from a near horizontal ("open") to a near vertical position ("shut").
Historically, the enclosure was operated by the use of the Ratchet Swell lever, a lever that locks into two or three positions controlling the opening of the shutters. Many Ratchet Swell devices were replaced by the more advanced Balanced pedal because it allows the enclosure to be set at any point.
In addition, an organ may have a crescendo pedal, which would be found to the right of any expression pedals, and similarly balanced. Applying the crescendo pedal will incrementally activate the majority of the stops in the organ, starting with the softest stops and ending with the loudest, excluding only a handful of specialized stops that serve no purpose in a full ensemble. The order in which the stops are activated is usually preset by the organ builder and the crescendo pedal serves as a quick way for the organist to get to a registration that will sound attractive at a given volume without choosing a particular registration, or simply to get to full organ. Most organs also have a piston and/or toe-stud labeled "Tutti" that activates full organ.
Read more about this topic: Organ Console
Famous quotes containing the word expression:
“Parents do not give up their children to strangers lightly. They wait in uncertain anticipation for an expression of awareness and interest in their children that is as genuine as their own. They are subject to ambivalent feelings of trust and competitiveness toward a teacher their child loves and to feelings of resentment and anger when their child suffers at her hands. They place high hopes in their children and struggle with themselves to cope with their children’s failures.”
—Dorothy H. Cohen (20th century)