The chambers are rooms containing the sound-producing parts of the organ - pipe work and percussions - and associated items like wind chests, regulators, building frames etc.

The organ speaks from the chambers into the auditorium via the shutters (very occasionally, a chamber used for percussion, 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 greatly.