An adjective which refers to an octave scale of 12 roughly semitonal intervals such as 12-tone equal temperament.
In the definition above, 12-EDO is an example of a chromatic scale where the between-degree intervals are all exactly Semitones. Other examples which always have 12 pitches, but with semitones whose sizes vary slightly, would be any of the temperaments ordinaires or any of the well-temperaments. Still other examples would be 12-tone subsets of linear temperaments which theoretically could go on infinitely, such as meantones or pythagorean tuning; in both of these cases, limiting the series to 12 pitches gives roughly semitonal intervals between degrees. The chromatic scale arose as an entity during the 1300s, within a pythagorean context.
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