Tonal functions · The chords of a key · Music theory
Chords are grouped by their function, the role they play in the key. The tonic (I) is rest. The dominant (V, and also VII) is the tension that asks to…
Tonal functions
Chords are grouped by their function, the role they play in the key. The tonic (I) is rest. The dominant (V, and also VII) is the tension that asks to return to the tonic, because of the leading tone. The subdominant (IV, and also II) moves away from the tonic and prepares the dominant.
VI and III share notes with I and can act as tonic. The most common path of a phrase is tonic, subdominant, dominant and tonic: I – IV – V – I.
How chords are linked
Functions explain the course of a phrase: leave the tonic, prepare the dominant and return. Hugo Riemann formulated these three functions in 1893. Chords that share two notes can substitute for each other: VI acts as tonic and II, as subdominant.
The motion of the bass also counts. The strongest is a descending fifth, as in V–I or II–V, which is why the chain VI–II–V–I sounds so natural: it is a fragment of the circle of fifths. Whole works are built by linking this turn.