in Music, a musical interval, by which most authors who have written on the theory of music use to express the octave of the Greeks.

among the musical-instrument-makers, a kind of rule or scale whereby they adjust the pipes of Diapason organs, and cut the holes of hautboys, flutes, &c. in due proportion for performing the tones, semitones, and concord, with precision.

DIAPASON Diatessaron, in Music, a kind of compound concord, whereof there are two sorts; the greater, which is in the proportion of 10:3; and the lesser, in that of 16:5.

DIAPASON Diapente, in Music, a compound conso- nance in a triple ratio, as 3:9. This interval, says Martianus Capella, consists of 9 tones and a semitone; 19 semitones, and 38 dieses. It is a symphony made when the voice proceeds from the first to the twelfth sound.

DIAPASON Diatessaron, in Music, a compound con- cord founded on the proportion of 8 to 3. To this in- terval Martianus Capella allows 8 tones and a semi- tone; 17 semitones, and 34 dieses. This is when the voice proceeds from its first to its eleventh sound. The moderons would rather call it the eleventh.

DIAPASON Ditone, in Music, a compound concord, whose terms are as 10:4, or as 5:2.

DIAPASON Semiditone, in Music, a compound con- cord, whose terms are in the proportion of 12:5.