Hexachord

In music, a hexachord is a collection of six tones. The term was originally used in the Middle Ages, but gained new currency in the 20th century with the development of musical set theory.

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The basis of most if not all medieval European music theory is the hexachordal system. This system attempted to explain the pitch relationships in the music of the time by grouping pitches into sets of six, or hexachords. In each hexachord, all adjacent pitches are a whole tone apart, except for the middle two, which are separated by a half tone. In each hexachord, these pitches are called ut, re, mi, fa, sol, and la, so the half tone is always between mi and fa. Note that most pitches have several syllables associated with them, one for each hexachord they belong to. These syllables were often used to disambiguate octaves: thus, C was "C fa ut" (or "Cefaut"), c was "C sol fa ut", and cc was "C sol fa". Since the lowest pitch was designated by the Greek letter Γ (gamma), it was known as "Gamma ut" or "Gamut". This term came to designate the whole system, and later extended its meaning outside music to denote an entire range of anything.

Music: Music is a natural intuitive phenomenon operating in the three worlds of time, pitch, energy, and under the three distinct and interrelated organization structures of rhythm, harmony, and melody....

Collection: In common usage, a collection is any group of items that has one or more properties in common, usually brought together for some specific purpose. See Collecting and Collectibles....

Tone: The word tone is used in several different fields with different meanings....