semitone(redirected from Pythagorean diatonic semitone)
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the smallest interval in European music. In the modern system of temperament, all semitones are equal, and there are 12 semitones in an octave.
There are three types of semitones: diatonic, chromatic, and enharmonic. The diatonic semitone is an interval between adjacent steps of a scale (for example, B to C, D to E flat [a minor second]). The chromatic semitone is the interval between a foundation and its raised or lowered variant (for example, F to F sharp, an augmented prime). The enharmonic semitone is the interval formed by the alteration of adjacent steps—for example, F double sharp to A flat, a double-diminished third (seeINTERVAL).