Pipe Organ

The pipe organ is a musical instument commonly used in churches or cathedrals that produces sound by driving pressurized air (called wind) through pipes selected via a keyboard. Because each organ pipe produces a single pitch, the pipes are provided in sets called ranks, each of which has a common timbre and volume throughout the keyboard compass.

Stops
Most organs have multiple ranks of pipes of differing timbre, pitch and loudness that the player can employ singly or in combination through the use of controls called stops.