Diapason

Di'apase, (dī-a-pā'zn.) [From Gr. dia, through, and pa son, all-that is, through all the notes of the octave.] (Mus.) An interval which most authors who have written upon the theory of music use to expre the octave of the Greeks. The D. is the first and most perfect of the concords: if considered simply, it is but one harmonic al interval; though, if considered diatonically, by tones and semitones, it contains 7degrees. Also, the fundamental or standard scale by which musical instruments are made. [s. 284]