The basic sound of the Theatre Organ is produced by organ pipes located in each chamber.
The selection and layout of pipes is part of the musical design of the instrument; although each organ builder will have their own approach to the details of pipe construction, the basic principles are common with the pipework dividing into the three families of reeds, flues and (rather a speciality of the theatre organ) diaphones.
Organ pipes come in sets – in classical organs called a ‘stop’, or in theatre organs called a ‘rank’. Each pipe in a particular rank or a stop produces a note of the same tone colour, with a pipe for every note. The section on Extension and Unit organs explains this further.