Topic summary
Functional harmony
Extracted from the Wikipedia article Function (music).
Contemporary functional harmony
Beyond the original German theory, the functions of tonic, dominant, and subdominant have been extrapolated to other chords, in which those with tonic function are most stable and resolved; dominant function, least stable and resolving to the tonic; and subdominant (or pre-dominant) function, somewhere in between and often setting up another chord with dominant function.