Decode a symbol from left to right
Begin with the root letter and accidental. The next mark establishes quality: a bare root normally means major; m means minor; dim or ° means diminished; aug or + means augmented. A following number normally names the highest member of a third-based extension, while add introduces a tone without implying the intervening seventh.
Alterations such as ♭5, ♯5, ♭9 and ♯11 modify one stated degree. “no3” or “omit3” removes a tone. A slash then names the required bass: C/E is a C-major chord with E below the other chord tones, while D/C places C under a D-major triad.
Five seventh symbols that must not be confused
C7 is C–E–G–B♭: a major triad plus minor seventh. Cmaj7 is C–E–G–B: both triad and seventh are major. Cm7 is C–E♭–G–B♭. Cdim7 is C–E♭–G♭–B𝄫, whose diminished seventh spelling is structural even though B𝄫 shares a piano key with A. Cm7♭5 is C–E♭–G♭–B♭ and is also called C half-diminished seventh.
The word “major” beside 7 applies to the seventh, not merely to the triad. The plain 7 symbol means dominant-seventh quality. These distinctions are small on the page and large in pitch content, so the complete note answer remains beside every symbol.
- C7 — 1–3–5–♭7 — C–E–G–B♭
- Cmaj7 — 1–3–5–7 — C–E–G–B
- Cm7 — 1–♭3–5–♭7 — C–E♭–G–B♭
- Cdim7 — 1–♭3–♭5–𝄫7 — C–E♭–G♭–B𝄫
- Cm7♭5 — 1–♭3–♭5–♭7 — C–E♭–G♭–B♭
Triads, suspended chords and added notes
Major, minor, diminished and augmented triads are distinguished by their thirds and fifths. Suspended symbols remove the third: Csus2 is C–D–G and Csus4 is C–F–G. In modern chord notation “sus” often labels that pitch set directly; in historical counterpoint a suspension also describes a prepared dissonance and its resolution, so the two uses should not be silently treated as identical.
Cadd9 is C–E–G–D and does not imply B♭. C9 normally includes the dominant seventh: C–E–G–B♭–D. “Add2” and “add9” can describe the same pitch class in different registers, but the chosen label may signal intended spacing. C6 and Am7 share C–E–G–A as pitch classes; bass, context and function determine the useful name.
Extensions, omissions and practical piano voicing
Ninth, eleventh and thirteenth symbols extend a stack of thirds and normally imply a seventh. C11 conceptually continues through D and F; C13 continues through A. On piano, playing every theoretical tone in one close cluster can obscure the quality, so practical voicings often omit the perfect fifth, spread the register or place the root in another instrument.
An omission changes the performed voicing, not the full spelling of the symbol’s theoretical structure. An altered extension must remain explicit: C7♭9 changes D to D♭, while C7♯11 changes F to F♯. ChordMetric’s explorer shows the complete formula; it does not claim that one close-position result is the only playable arrangement.
ASCII, Unicode and publisher variants
Input may use C# or C♯, Bb or B♭, dim or °, and m7b5 or m7♭5. Those pairs are interface aliases, not different chords. Publishers also vary between maj7, Δ7, min7, m7, ø7 and m7♭5. A parser should normalise an accepted alias while showing the user exactly which standard name and note set it resolved to.
A capital M can be ambiguous in unfamiliar typefaces, and a hyphen sometimes means minor in jazz-oriented notation. ChordMetric therefore favours explicit plain-language quality names beside compact symbols and never treats typography alone as proof of an answer.
A reliable decoding check
Write the symbol in five fields: root, quality, extension or added tone, alteration or omission, and bass. Build the complete formula, assign required chord letters, calculate accidentals, then apply the slash bass without changing the chord identity. Finally compare the accepted symbol, plain-language name and notes in the explorer.
For E♭maj9/G, the fields are E♭ root, major-seventh quality, ninth extension and G bass. The complete tones are E♭–G–B♭–D–F; placing G lowest makes first inversion. No copied song or voicing is needed to verify the grammar.