Build Progressions with Diatonic Chords: Function and Cadence
Why do in-key chords sound natural together? Learn the T-SD-D functions, why same-function chords swap freely, and how cadences end a progression. Hear it in the tool.
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Build Progressions with Diatonic Chords: Function and Cadence
If you just want the steps, four decisions is enough. This article goes one level deeper: why in-key chords sound natural together, explained through function (T, SD, D) and cadences. Understand the mechanism and you can choose substitutions and endings on purpose.
First, hear the functions
In the Diatonic Chord Tool, set C major and play these in order:
C(restful — the tonic, T)G(tense — the dominant, D)C(back home, resolved)
T → D → T: leave, strain, return. That pull is the backbone of every progression.
Three functions, and why chords swap
The seven chords of C major fall into three functional groups:
| Function | Chords | Role |
|---|---|---|
| Tonic (T) | C, Em, Am | landing, stability |
| Subdominant (SD) | F, Dm | moving away |
| Dominant (D) | G, Bdim | maximum tension, wants to resolve |
Chords in the same group can be swapped without breaking the flow. That’s what “sounds natural” really means. Take C→F→G→C, swap C for Am (also T) and F for Dm (also SD): Am→Dm→G→C. The chords change, but the T→SD→D→T skeleton holds, so it never falls apart.
How it ends: cadences
A progression’s impression is set mostly by its last two chords — the cadence. Compare them in the tool:
| Cadence | Last two chords | What it sounds like |
|---|---|---|
| Perfect | V → I (G→C) | a clear “we’ve arrived” |
| Plagal | IV → I (F→C) | a soft, hymn-like landing |
| Deceptive | V → VIm (G→Am) | sounds final, then keeps going |
Play G→C then G→Am back to back: one different final chord flips “close” into “continue.” End a chorus on a perfect cadence for a hard stop, or a deceptive cadence to pull into the next section.
Handling the tense chord (Bdim)
VIIdim (Bdim) is the most unstable chord, used as a path toward I rather than a resting point. Slipping it in just before resolution — Dm→Bdim→C — works well.
Common stumbles
- Ending without passing through the dominant (G) → a weak close
- Staying on one function too long → no motion (cycle T→SD→D)
- Ignoring the cadence → a progression that just “sort of stops”
What to try next
Take C→F→G→C and swap only the last two chords through perfect → plagal → deceptive. Most of the chords stay the same, yet the ending changes how the whole thing breathes.
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