Chroma
- This page is about chromas in general. For the chroma in the diatonic scale, see Chromatic semitone.
The chroma (precisely the moschroma) of a mos scale is the interval that is the difference between the large step and the small step in the scale. In particular, the chroma in the diatonic scale is the chromatic semitone, or augmented unison, such as the interval of C–C♯.
In staff notation, alteration by the chroma can be represented by the sharp (♯) or flat (♭), as is shown above. In diamond-mos notation, it should be noted that they are reserved exclusively for the diatonic scale, whereas am (&) and at (@) are used for other mos scales.
Moving one note in a mos scale by a chroma leads to a modmos scale if the result is not just a transposition of the original mos scale.
The Fokker block, being a generalization of the mos scale to higher ranks, also has the concept of chroma. See Fokker block.
History
The first mention of the term "chroma" occurs in Marchettus of Padua[1] where he describes it as an interval smaller than the diatonic semitone. The exact nature of the interval he was describing is debated.[2]
In psychoacoustics
In psychoacoustics, the term chroma refers to the circular perception of pitch with respect to octave equivalence. This is essentially the same as the concept of pitch class.
See also
- Pythagorean chroma
- Chromatic semitone
- 25/24, the 5-limit chromatic semitone
- Sharpness, a property related to sharps and flats in edos
- Diesis (scale theory)
References
- ↑ Marchettus of Padua (1318) Lucidarium.
- ↑ Joe Monzo (2008) Speculations on Marchetto of Padua's "Fifth-Tones". http://www.tonalsoft.com/monzo/marchetto/marchetto.aspx