Our organ will actually be 4 instruments in one (each, a “division“).  3 are played from the 3 keyboards (“manuals“), each with 61 notes, and the fourth is played by the feet on the pedalboard, with 32 notes.

Each division is a set of pipes which sits on a box of compressed wind (a “windchest“) supplied by an electric blower. The wind is stored in large bellows (“reservoirs“) made of wood and sheepskin, which keep the wind at even pressure. Pressing a key operates a mechanism that allows the wind into a pipe or several pipes, so producing the sound. Normally there is one pipe per note for each different sound.

The organ has a variety of different sounds produced by pipes of different shapes, sizes and materials. Pipes that produce the same quality of sound are placed in rows in the wind chest (“ranks“).  Each rank is operated by a white knob (or “stop“) on the console.

The organ makes several different sounds.  There is the sound that is unique to the organ – the “diapason” or “principal”, and each manual has its own principal chorus of ranks that sound at several pitches.  There are also pipes that imitate flutes and other woodwind sounds, strings and brass.  So with one pipe per note for each type of sound each division contains several hundred pipes.

The organist sits at the console and the console is linked to the pipes by the key action. Our organ will have 2 types of action:

Direct Electric Action – electrical relays and magnets are used to operate small spring-loaded stoppers that allow wind into each pipe (this will be used mainly on the pedal division).

Electro-Pneumatic Action – the connection from the key to the inside of the windchest is by electrical relay which activates a pneumatic motor (a small bellows made of wood and sheepskin) which, in turn, pulls down a wooden and felt “pallet” which allows wind into the pipes (mainly used on the manual divisions).

For each stop at All Souls there is another type of pneumatic motor which pulls a “slider” into position. This is a thin strip of wood with holes in which, when it is in position, line up with matching holes in the top of the windchest so that wind can enter all of the ranks of pipes whose sliders are in position.

There are some 450 pneumatic motors inside the organ, all of which have been either made or restored by hand.