HEXACHORD
Etymology
Noun
hexachord (plural hexachords)
(music) A series of six tones denoted with the syllables ut-re-mi-fa-sol-la separated by seconds, the only of which that is a minor second being mi-fa.
Usage notes
• The above definition dates back to the theory of Guido of Arezzo (11th century)
Source: Wiktionary
Hex"a*chord, n. Etym: [Hexa- + Gr. hexacorde.] (Mus.)
Definition: A series of six notes, with a semitone between the third and
fourth, the other intervals being whole tones.
Source: Webster’s Unabridged Dictionary 1913 Edition