DIAPASON , a term in music, originally for an interval of an octave. The Greek is an abbreviation of , a consonance through all the tones of the scale. In this sense it is only used now, loosely, for the compass of an instrument or voice, or for a harmonious melody. The name is given to the two foundation stops of an organ, the open and the stopped diapason (see Organ), and to a standard of musical pitch, as in the French diapason normal (see Pitch, Musical).
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)