Definition
A diapason stop is a control on a pipe organ that activates the set of diapason pipes. Activating this stop brings forth the fundamental, foundational sound of the organ. It's like pressing the 'classic' button on a sound system. The diapason stop is essential for producing the characteristic full and rich tone of the organ. This stop gives the organ its fundamental sound, and is often used to accompany hymns and other classical music.