Organ stop in the context of Hammond organ

An organ pipe is a sound-producing element of the pipe organ that resonates at a specific pitch when pressurized air (commonly referred to as wind) is driven through it. Each pipe is tuned to a note of the musical scale. A set of organ pipes of similar timbre comprising the complete scale is known as a rank; one or more ranks constitutes a stop.

The pipe organ is a musical instrument that produces sound by driving pressurised air (called wind) through the organ pipes selected from a keyboard. Because each pipe produces a single tone and pitch, the pipes are provided in sets called ranks, each of which has a common timbre, volume, and construction throughout the keyboard compass. Most organs have many ranks of pipes of differing pitch, timbre, and volume that the player can employ singly or in combination through the use of controls called stops.

A pipe organ has one or more keyboards (called manuals) played by the hands, and most have a pedalboard played by the feet; each keyboard controls its own division (group of stops). The keyboard(s), pedalboard, and stops are housed in the organ's console. The organ's continuous supply of wind allows it to sustain notes for as long as the corresponding keys are pressed, unlike the piano and harpsichord whose sound begins to dissipate immediately after a key is depressed. The smallest portable pipe organs may have only one or two dozen pipes and one manual; the largest pipe organs can have over 33,000 pipes and seven manuals. A list of some of the most notable and largest pipe organs in the world can be viewed at List of pipe organs. A ranking of the largest organs in the world—based on the criterion constructed by Michał Szostak, i.e. 'the number of ranks and additional equipment managed from a single console'—can be found in the quarterly magazine The Organ and in the online journal Vox Humana.

The musical instrument known as the regal or regalle (from Middle French régale)is a small portable organ, furnished with beating reeds and having two bellows. The instrument enjoyed its greatest popularity during the Renaissance. The name "regal" was also sometimes given to the reed stops of a pipe organ, and more especially to the vox humana stop.

The pipe organ is played from an area called the console or keydesk, which holds the manuals (keyboards), pedals, and stop controls. In electric-action organs, the console is often movable. This allows for greater flexibility in placement of the console for various activities. Some very large organs, such as the van den Heuvel organ at the Church of St. Eustache in Paris, have more than one console, enabling the organ to be played from several locations depending on the nature of the performance.

Controls at the console called stops select which ranks of pipes are used. These controls are generally either draw knobs (or stop knobs), which engage the stops when pulled out from the console; stop tablets (or tilting tablets) which are hinged at their far end; or rocker-tablets, which rock up and down on a central axle.

Clarion is a name for a high-pitched trumpet used in the Middle Ages and the Renaissance. It is also a name for a 4' organ reed stop that produces a high-pitched or clarion-like sound on a pipe organ in the clarion trumpet's range of notes.

The word clarion has changed meanings over centuries and across languages. Today, in modern French clairon refers to the bugle, while in Italy chiarina refers to modern trumpets of historic design, made from bent tubing and without valves, similar to the natural trumpet. Resembling these instruments is the modern fanfare trumpet, like the chiarina or natural trumpet, but with the option of using valves.