Tonic, Subdominant, and Dominant: Chord Functions

Every diatonic chord plays a role — a “function” — in the emotional story of a piece of music. Those functions are grouped into three categories: Tonic (T), Subdominant (SD), and Dominant (D).

The Three Functions

Tonic (T) — Stability and Home

Tonic chords feel resolved and at rest. They’re where a phrase can comfortably end.

In C major: I (C), IIIm (Em), VIm (Am)

Subdominant (SD) — Movement and Departure

Subdominant chords create a sense of gentle movement away from home — neither fully tense nor fully resolved.

In C major: IIm (Dm), IV (F)

Dominant (D) — Tension Seeking Resolution

Dominant chords create strong tension that wants to resolve back to the tonic. The V chord (especially as V7) is the classic example.

In C major: V (G), VIIdim (Bdim)

How Functions Create Progressions

Chord progressions work by moving through these functions in emotionally meaningful sequences:

• T → SD → D → T — the classic cadential pattern: home, departure, tension, resolution
• T → D → T — direct: home, tension, back home
• SD → D → T — a common ending pattern (the “authentic cadence”)

Understanding functions means you stop thinking about individual chords and start thinking about emotional arcs.

Example: The Same Function in Different Keys

The T → SD → D → T arc in C major: C – F – G – C

In A major, the same arc becomes: A – D – E – A

In Eb major: Eb – Ab – Bb – Eb

Same function, different sound. This is why musicians talk about keys in terms of Roman numerals and functions — it’s universal.

→ See chord functions in the diatonic tool