A Dictionary of Music and Musicians/Diesis

DIESIS, from the Greek δίεσισ which means division, and was the name given to quarter tones in their system. Aristotle takes it as the unit of musical tones, the last subdivision of intervals. In modern acoustics it means the interval which results from the two sounds which are arrived at by tuning up 3 perfect thirds and an octave, which is the same as the difference between a major or diatonic semitone, and a minor or chromatic semitone, the ratio of their vibrations being 125:128. It is commonly called the Enharmonic Diesis, enharmonic being the word which is applied to intervals less than a semitone.

Diése has been adopted by the French as their term for sharp.

[ C. H. H. P. ]