What are chord functions?
A chord function is its role within a key. It determines whether a chord creates a sense of rest, motion or tension. The three main functions are: tonic (T), subdominant (S) and dominant (D).
Tonic (T)
The tonic is the chord of rest — the "home" of a key. In major, tonic chords are degrees I, iii and vi. Progressions naturally gravitate back to the tonic.
Subdominant (S)
The subdominant creates departure from the tonic. Degrees IV and ii are typical subdominants. The subdominant often precedes the dominant (S → D → T).
Dominant (D)
The dominant creates maximum tension and pull toward the tonic. Degree V is the primary dominant. vii° also serves a dominant function because it contains the tritone.
Functional flow
The classic functional flow is: T → S → D → T. This is the foundation of most progressions in pop, classical and jazz music.
- T → S: departure from rest
- S → D: building tension
- D → T: resolution