Hexatonic
A hexatonic scale is a scale with 6 tones per equave.
Hexatonic MOS scales may be found at: Hexatonic MOS.
Other hexatonic scales may be found at: Category:6-tone scales.
Hexatonic scales may sometimes be used as chords rather than scales, in which case they are called hexads.
“Equihexatonic” scales are scales with 6 roughly equally spaced tones per octave. Equihexatonic scales are rare in the world’s musical traditions, with one big exception: the whole tone scale of modern Western music. It is an equihexatonic scale, so equi-, in fact, that it is exactly 6edo.
6 equal frequency divisions instead of pitch gives the hexatonic overtone scale, the first mode of 6afdo.
Although equihexatonic scales may be rare, unequal hexatonic scales occur fairly commonly in the world’s musical traditions, especially in the folk music of some parts of Europe.
The folk music of some parts of Croatia often uses a 6-tone just intonation scale called the Istrian scale. It uses an unequal tuning, best approximated as a 6-tone subset of 7ifdo (subharmonics 7 to 14).
The folk music of Scotland and Ireland often uses a 6-tone scale which can be arrived at by stacking perfect fifths with an octave period, which depending on the mode used may be called the “Scottish hexatonic” scale, the “hexatonic minor” scale or other names. Historically, the tuning varied, though today it is usually (but not always) tuned to 12edo.
Outside of Europe, in late 19th-century America, the “minor blues” and “major blues” scales were developed. They have since seen widespread worldwide use across many genres of popular music in the 20th and 21st centuries. Often, these scales will be used flexibly, as the first building block of a larger scale, or as their own scale but with heavy chromaticism. Most often these scales are used within a 12edo context, however they may, especially in their original blues-genre context, make use of “blue notes”, where the pitch of a scale degree is bent away from the 12-tone grid to some other interval, which may be only slightly xenharmonic, or very xenharmonic, in its character, varying from performance to performance and within the same performance. Some xenharmonicists have been inspired by the minor and major blues scales to create new scales, such as antipental blues.
Curiously, the Scottish hexatonic, hexatonic minor, minor blues and major blues scales are all constructed by adding one note to a 2L 3s MOS scale. It is curious that they share this common structure - but also useful, as it suggests that maybe, even outside of 12edo, adding a note to 2L 3s could be a productive way of developing useful hexatonic scales in any tuning which supports that MOS (including most EDOs).