A numeral says where a chord sits in the key. Its role is what your ear expects next: some chords sit at home, some pull, and one, the V, points straight at home.
Every chord has a role
Each row plays the same setup, I · IV · V, then lands on its chord. The higher a landing sits on the hill, the harder it pulls back toward I.
ChordRoleWhat it does
HomeA phrase can end here.
AwayAway from home. Sets up V.
TensionPulls back toward I.
Progressions are named by these roles, not by pitches.
How often each chord shows up
In 292 Billboard hits from 1958 to 1971, I, IV, and V each appeared in about nine songs of ten. The other four chords appeared in far fewer.
ChordSongs using itRoughly
Counted as songs that use the chord at least once, not how often it plays. Newer pop ranks the same way: I, IV, V, and vi lead, then ii, then iii.
Keep the three
I, IV, and V carry the three roles between them: home, away, strongest pull. The rest of this unit runs on those three. Unit 6 brings the other four back.
Why V pulls: the leading tone
Why does V pull so hard? It holds ti, the note one half step under do, the leading tone from 2.3. Hear the lean by itself, then inside the chords.
B · ti, leaning C · do, home
Game · Home or hanging?
1 / 5
A short phrase. Did it land home on I, or stop hanging on V?