Chord Symbols Decoded: What m, 7, maj7, sus4, and add9 Actually Mean
The short answer: A chord symbol is a recipe. The capital letter is the root. Everything after it modifies a default recipe of root–3rd–5th (a major triad): m lowers the 3rd, numbers add scale degrees, sus replaces the 3rd, dim/aug bend the 5th. Once you know the default, every symbol is a one-word edit to it.
The decoder table
| Symbol | Recipe | In C | Sound |
|---|---|---|---|
C | 1–3–5 | C–E–G | major, home |
Cm | 1–♭3–5 | C–E♭–G | minor, sad |
C5 | 1–5 | C–G | power chord, neutral |
C7 | 1–3–5–♭7 | C–E–G–B♭ | bluesy, restless |
Cmaj7 | 1–3–5–7 | C–E–G–B | jazzy, dreamy |
Cm7 | 1–♭3–5–♭7 | C–E♭–G–B♭ | mellow |
Csus2 / Csus4 | 3rd → 2 or 4 | C–D–G / C–F–G | floating, unresolved |
Cadd9 | 1–3–5 + 9 | C–E–G–D | shimmery major |
Cdim / C° | 1–♭3–♭5 | C–E♭–G♭ | anxious |
Caug / C+ | 1–3–♯5 | C–E–G♯ | floating up |
C/E | C chord, E lowest | E under C–E–G | slash chord |
The three rules that generate the table
1. Bare number = add the flat 7 first. C7 doesn't mean "add a 7" — it means the dominant recipe: major triad plus ♭7. To get the pretty natural 7 you must say maj7. This is the single most confusing convention in music notation, and the maj7 / m7 / dom7 triangle is worth ten minutes on its own.
2. m touches only the 3rd. Minor-ness lives entirely in the third. Cm7 = minor 3rd and flat 7; Cmmaj7 (rare, spooky) = minor 3rd with natural 7.
3. add means add — nothing else. Cadd9 is a plain major triad plus a 9th (D, the 2 an octave up). C9 without "add" implies the whole dominant stack underneath (1–3–5–♭7–9). Small word, big difference.
Here's rule 1's poster child, Cmaj7, in its open-position form — the same C shape you know with one finger lifted:
Stop memorizing, start spelling
The payoff of reading symbols as recipes: you can build chords you've never seen. Handed Fadd9? Spell it — F, A, C, plus G — and find those notes wherever your hand already is. That beats owning a 4,000-chord dictionary, because the dictionary can't tell you which voicing is near your current position; spelling can.
Frequently asked questions
What's the difference between C7 and Cmaj7?
They differ by one note and a lot of mood. Cmaj7 has the natural 7th (B) — soft and jazzy. C7 has the flat 7th (B♭) — bluesy and tense; it's a dominant seventh chord. The plain number always means the flat seventh; "maj" refers to the 7th, not the chord's third.
What does the "m" in Am mean?
Minor — specifically, a minor third instead of a major third above the root. No letter after the root means major. Everything else in a chord symbol modifies one of those two starting points.
What does a slash chord like G/B mean?
"G chord, B in the bass" — the chord before the slash, the bass note after it. Usually it's an inversion used to make the bassline walk smoothly; the full story is in Slash Chords and Inversions.
What do "sus" and "add" mean?
Sus replaces the third with its neighbor (sus2 or sus4 — see sus chords explained); add keeps everything and stacks one more note on top (add9). Replace vs. append — that's the entire difference.