Ramsay
"The notes as they naturally arise from unity have different degrees of development, and according to the degree of development of each note is its specific levity or gravity. The three notes which form the subdominant chord have different degrees of gravity; the three which form the dominant chord have different degrees of levity. The remaining note is the center of the tonic chord -

[Scientific Basis and Build of Music, page 95]

See Also

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evolution
growth
biological process of development
common developmental axis
degree of development
development
development of trinities
development-enhancing function
development-impeding
developmental process
developmental product
form of development
mode of development
precondition for development
regressive development
spiritual development
Stages of Soul Development