Commentary for Teachers

6 Organ Design

The diagram shows the structure of an organ with a console which is detached from the main working parts.  All the keys and stops are linked by electric cables which activate electromagnets to control the supply of air to the pipes. On a mechanical action organ, the keys would be connected directly to the individual pipes by a system of levers.

♪ What happens to the sound of the Swell organ as the Swell Box is opened or closed?

The loudness varies as the Swell box is opened or closed.

♪ Describe the main differences in the sounds made by the Great, Swell and Pedal organs.  

The shutters on the Swell box work like slotted blinds.  In this example, each shutter swivels about a vertical axis.  In some organs the axes are horizontal. The Swell box is designed to allow the loudness of the Swell pipes to be varied in a smooth continuous way.  The Great pipework is not enclosed at all, so there is no control of the loudness of a rank of pipes.

The photo shows the organ in the Church of St Peter Mancroft, Norwich.  

♪ The large towers contain the pipes for which part of the organ?

The towers contain the large pipes for the Pedal division.