There are very few things in music which have not change written upon them. TWELVE and THREE, however, are stable. There is nothing that will disturb the propriety of the circle of twelve fifths, as in the tempered system of music; for, although the mathematical-intonation indulges in thirteen keys, the thirteenth is simply the first of a new cycle of twelve.
The working model of three fifths is that which possesses musical life-powers; and these life-powers go with it wherever it goes, and they go with nothing else. [Scientific Basis and Build of Music, page 74]
See Also
7.22 - Thirteenth
Keeper of the Keys
key
progression of keys
Ramsay - PLATE VII - The 24 Keys and their Chords
Ramsay - PLATE X - Growth-like Continuity of Chords and Keys
Ramsay - The Closed System of the Twelve Keys
Ramsay - The New Notes of New Keys and their Service
thirteen pairs
thirteenth scale
twelve keys
twelve major keys
twelve minor keys
twice twelve-fold family of keys