The chambers are rooms containing the sound-producing parts of the organ - pipework and percussions - and associated items like windchests, regulators, building frames etc.
The organ speaks from the chambers into the auditorium via the shutters (very occasionally, a chamber used for percussions, bass pipes etc. may not have shutters).
Theatre organs are generally totally enclosed in chambers; small and medium-sized instruments in one or two chambers and the largest instruments perhaps in three or four chambers, although there are no hard-and-fast rules.
Chambers should be constructed and positioned so that they are reasonably soundproof, but so that the sound is projected into the auditorium when the shutters are opened. For a medium-sized instrument, the two typical chambers would each be 12 to 14 feet wide, 11 feet high and about 8 to 10 feet deep. These dimensions and proportions can vary, although low headrooms can present considerable problems.
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