Tuning Enharmonics
In principle, the modern musical use of the word enharmonic to mean identical tones is correct only in equal temperament, where the octave is divided into 12 equal semitones; but even in other tuning systems enharmonic associations can be perceived by listeners and exploited by composers. This is in contrast to the ancient use of the word in the context of unequal temperaments, such as quarter-comma meantone intonation, in which enharmonic notes differ slightly in pitch. It should be noted, however, that enharmonic equivalents occur in any equal temperament system, such as 19 equal temperament or 31 equal temperament, if it can be and is used as a meantone temperament. The specific equivalences define the equal temperament. 19 equal is characterized by E♯ = F♭ and 31 equal by D = F, for instance; in these tunings it is not true that E♯ = F♮, which is characteristic only of 12 equal temperament.
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