Pipe organs have worked the same way for nearly two thousand years. Air is blown into the pipe organ, stored in reservoirs, and delivered to windchests upon which the pipes sit.
When an organ's key is depressed, it causes a panel to open in the windchest, allowing air to be blown through a given pipe. In pre-electricity days, air was pumped by hand. Nowadays electric blowers do the pumping.
The pipes, from 32 feet to smaller than a pencil, are made of various materials to produce a variety of tone qualities. The largest pipes that produce booming bass notes are made of wood and metal, and can be up to thirty-two feet long.
The size or scale of the pipe determines its tone quality and intensity. Other pipes are made of different combinations of metals such as tin and lead alloys, zinc and copper.
Some pipes are designed to mimic various instruments. Flue pipes, for example, work like a whistle; air rushing over a lip in the pipe can be made to produce flute-like tones. Reed pipes work like clarinets; air flows by a reed that vibrates to produce sound.
These pipes can be adjusted to sound like anything from a trumpet to a trombone. Pipe organs are assembled by hand in workshops, and no two are exactly alike.