A keyboard instrument that is sounded by air moving through pipes.

The pipe organ usually has several manuals as well as pedals that control the air flow through combinations of pipes. A rank of pipes constitues one stop and consists of a row of pipes, one for each key on the keyboard.

Organ pipes come in a variety of sizes, shapes, materials, and methods of setting the air columns to vibrate. The pipes can range in size from a quarter-inch in length to over 32 feet with the shorter pipes creating the higher pitches and the larger pipes creating the lowest pitches. Organ pipes can be any shape from round to square, conical to cylindrical, or from straight to curved. The differing shapes provide a variety of tone colors. The pipes are typically constructed from either wood or metal. These materials provide another factor in the tone color of the pipe.

The pipes are broken into two categories for creating sound, flue pipes and reed pipes.The flue pipes produce sound on the same principle of a whistle or recorder. The reed pipes produce sound on the same principle as the clarinet.

The pipe organ is an ancient instrument popular since the Medieval era. The use of organs is most commonly associated with religious music.

Small pipe organs were called 'positive' (easily placed in different locations) or 'portative' (small enough to carry while playing).