The Nashville Number System
Session musicians don't write "G – C – D" on their charts — they write "1 – 4 – 5". By numbering chords by their position in the key instead of by name, a whole song becomes instantly transposable: the singer wants it in a different key? Same numbers, new key, no rewriting. It's Roman numerals stripped down for the bandstand.
The Core Idea
Every major key has seven diatonic chords, one built on each scale degree. Number them 1 through 7. The quality is fixed by the key: 1, 4, 5 are major; 2, 3, 6 are minor; 7 is diminished. Once you internalise those qualities, a number chart tells you everything — and it works in any key.
The Numbers in Your Key
Key
Tap any number to hear its chord. The Roman numeral is shown below each — same concept, different notation.
Play a Number Progression in G
Countless rock & blues songs
"Let It Be", "With or Without You"
"Zombie", "Africa" feel
The jazz turnaround
Doo-wop / "Heart and Soul"
The Magic: One Chart, Every Key
Here's the 1 – 5 – 6 – 4 progression written once as numbers, then realised in four different keys. The numbers never change — only the letters do. That's why a Nashville chart works for any singer in the room.
| Key | 1 | 5 | 6m | 4 |
|---|---|---|---|---|
| C | C | G | Am | F |
| G | G | D | Em | C |
| D | D | A | Bm | G |
| A | A | E | F#m | D |
Reading a Number Chart
A bare number is the major/minor chord native to the key. 1 in G = G major; 6 in G = E minor.
A minus or "m" forces minor (2-); a triangle or "maj7" marks a major 7th; a diamond around a number means hold/let ring.
Theory class writes I–V–vi–IV; the studio writes 1–5–6–4. Upper/lowercase becomes a number plus a quality mark.
Build progressions by ear and number
Use the Chord Progression builder to drag chords into a sequence, or dig into why these numbers pull toward each other in Functional Harmony.