The Swell Shutters
The swell shutters form part or all of the chamber wall facing the auditorium, and the organ's sound passes through them. They resemble vertical or horizontal Venetian blinds, and can be opened or closed to control the volume of sound released into the auditorium.
In Wurlitzer and Christie organs, the swell shutters are opened and closed individually, or in linked pairs, as successive contacts are activated by the tilting pedals at the console.
In most Compton organs, all the swell shutters for a chamber are linked and they open together progressively in stages, operated by a pneumatic "whiffle-tree" motor, again controlled by the tilting pedal at the console. Compton fitted individual swell motors, similar to those on Wurlitzer and Christie organs, on some of their organs as a more expensive option. For dance and rhythmic music, where the swell shutters are used to give emphasis to certain notes, individual swell motors give faster response and better control.