Diesis Topics

• western harmony
• major thirds
• equal temperament
• octave
• theorists
• comma
• interval
• pairs
• musicians
• music

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Diesis, Diesis

In 12-tone equal temperament (on a piano for example) three major thirds in a row equal an octave, but three justly-tuned major thirds fall quite a bit narrow of an octave, and the diesis describes the amount by which they are short.

It is then the interval involved between pairs of notes which are enharmonic in equal temperament; for instance the interval between E and F, however large that is, is a diesis.

Being larger, this comma was termed "great" while the 128:125 comma was termed "lesser". But this "great diesis" is almost completely theoretical and almost never evoked in actual music, while the 128:125 "lesser diesis" is easily evoked and of great importance in Western harmony. Thus over time the term Great Diesis came to be frequently used for the 128:125 "lesser" comma. In short the terms are used in contradictory ways by various theorists and musicians.

Source: Wikipedia > Diesis