Tonic, subdominant, dominant
Name the three functions, their chords on degrees I, IV and V, and the role of each.
Three functions
In a key, chords play different roles: their functions. There are three main functions, each with its own triad:
- Tonic (T): the triad on degree I. Stability, rest, "home".
- Subdominant (S): the triad on degree IV. Moving away from the tonic, gently.
- Dominant (D): the triad on degree V. Tension that demands a return to the tonic.
The progression T – S – D – T is the model of most musical phrases: rest, departure, tension, return.
C major: T – S – D – T
Practice: A function in G major
Practice: A function in F major
Practice: A function in B♭ major
Three chords, the whole scale
Together, the T, S and D triads contain all seven notes of the scale. In C major:
- T: C, E, G;
- S: F, A, C;
- D: G, B, D.
So any note of a simple melody can be supported by one of the primary triads. C and G belong to two chords at once: C to the tonic and the subdominant, G to the tonic and the dominant.
The primary triads of C major: T, S, D
The function depends on the key, not on the chord. A C major triad is the tonic in C major, the subdominant in G major and the dominant in F major.