di·a·pa·son / ˌdīəˈpāzən; -sən/ • n. (also open diapason or stopped diapason) an organ stop sounding a main register of flue pipes, typically of eight-foot pitch. ∎ poetic/lit. the entire compass, range, or scope of something. ∎ fig. a grand swelling burst of harmony.
1. Greek name for the octave.
2. The name of certain org. stops which are the foundation tone of the instr. and are either ‘open’ or ‘stopped’ according to whether the ends of the pipes are clear or plugged (plugged stops are lower in pitch by an octave). open diapason, 8′, is the chief manual stop. There are also stopped diapason, horn diapason, and diapason phonon in which the lips of the pipes are leathered to refine the tone.
3. In Fr., diapason normal is a standard indication of pitch: A = 440 vibrations per sec.