chromatic

[Greek: "thru the colors" or "thru the shades"]

• 1. chromatic scale: An adjective which refers to an octave scale of 12 roughly semitonal intervals such as 12-tone equal temperament.

  See also chroma.

  [from John Chalmers, Divisions of the Tetrachord]

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  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.

  
  

• 2. chromatic genus: In ancient Greek theory, one of the three basic types of genus. It had a characteristic interval of approximately a "minor 3rd" at the top of the tetrachord, then 2 successive intervals of approximately a "semitone" at the bottom, making up the 4/3 "perfect 4th". [see also my Tutorial on ancient Greek tetrachord-theory]

  
  

• 3. chromatic semitone: In several different theories of the medieval, Renaissance, Baroque, and Classical periods, a distinction was made between chromatic and diatonic semitones, as there were two different sizes of semitone in many tuning systems. (Two good examples are Pythagorean and meantone.)

  The chromatic semitone is the interval between two notes of a scale which both have the same letter-name, but which have different accidentals (including the natural), for example, A - A#. The implication is that only one of the two is a bonafide diatonic scale degree. This interval is called the "augmented prime" and may be found abbreviated as aug1, #1, or +1 . See also diatonic.

  In the Pythagorean [3-Limit] system, the chromatic semitone is also called the apotome.

  Note that in positive systems (typical example: Pythagorean tuning), the chromatic semitone is larger than the diatonic, while in negative systems (typical example: any meantone tuning) it is exactly the opposite and the diatonic is the larger.

  Marchetto specified three types of semitone and called the third, naturally enough, the enharmonic; however, his names were matched with the intervals differently than in traditional theory.

  See also:

  tempering out the syntonic comma,
  diatonic

  [from Joe Monzo, JustMusic: A New Harmony]

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Updated:

2002.10.15
2002.1.8

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