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A card ‘Book’ of music, for a ‘Keyed’ system.
This one plays a 48 key organ.

A section of music from the 48 key book.

Music Book

Key

Compressed Air

Port to send/return air to/from a ‘Puff’

Outside Valve

Airflow Mode: (Exhaust=Key OFF, Pressure=Key ON)

The animation shows a cross section of a pressure operated keyframe (Not to scale).

When the key is passed through a hole in the card music, the outside valve closes, blocking the air ‘exhaust’ and the inside valve opens, feeding air, under pressure, to the port. This is connected via a length of tubing to the air inlet of a ‘puff’. This causes the puff to inflate and push a pallet inside the windchest, which causes air to pass to an organ pipe, producing a sound.

When the key is closed, the inside valve closes, blocking the feed of air and the outside valve opens. This causes the air in the puff to exhaust to atmosphere, deflating the puff and so closing the pallet, which stops the pipe from sounding.

There are two types of system, ‘Keyed’ and ‘Keyless’.

In a keyed system, a mechanical ‘key’ is placed under the punched card music. When a hole in the music passes over a key, it moves up through the hole and causes a valve (called a ‘Touch Box’) to open, which allows air to pass through to a small set of bellows (called a ‘Pneumatic Motor’ or ‘Puff’), which in turn pushes a ‘Pallet’ in the ‘Windchest’, allowing air to pass through an organ pipe, producing a sound.

Tubing to Windchest