The
pipe organ is a
musical instrument 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. Most organs have multiple ranks of pipes of differing timbre, pitch and volume that the player can employ singly or in combination through the use of controls called
stops.