Chord Symbol Guide

Naming, Writing, and Playing

Three related questions are easy to conflate: what are these notes called, what symbol should I write to suggest this chord, and what will a player do with what I wrote? This guide answers the first: given a set of notes, which symbol names them.

The other two allow more latitude. The notes D-G-A-C are exactly D7sus4, but a lead sheet might write D7sus, or even Dsus, trusting the reader to fill in the seventh. A performer, in turn, may voice any of these freely; jazz players will happily hang a seventh on anything.

Identification favors the precise name. Where a choice remains, we lean toward what a musician expects to read, not the loosest shorthand a setting allows.

Symbol Structure

A symbol has three parts:

Examples include C, Cm7, C13♭9, and Cmaj7 / E.

The root and bass are spelled to fit the current tonal context. The middle portion is formatted from the identified chord quality and extensions. Spelling and notation preferences, including enharmonic respellings chosen for convenience, change how the symbol looks without changing the underlying sense of root.

Two common notation styles are available. Before extensions and alterations are added, chord symbols start from these base quality labels:

Quality	Textual	Symbolic	Example
Major triad	no suffix	no suffix	C
Minor triad	m	−	Cm or C−
Diminished triad	dim	°	Cdim or C°
Augmented triad	aug	+	Caug or C+
Suspended triads	sus2, sus4	sus2, sus4	Csus4
Dominant seventh	7	7	C7
Major seventh	maj7	Δ7	Cmaj7 or CΔ7
Minor seventh	m7	−7	Cm7 or C−7
Minor-major seventh	m(maj7)	−Δ7	Cm(maj7) or C−Δ7
Half-diminished seventh	m7(♭5)	ø7	Cm7(♭5) or Cø7
Fully diminished seventh	dim7	°7	Cdim7 or C°7

In everyday practice these are not sealed systems; musicians often mix them, writing a dash for a minor chord but spelling out maj7, or reaching for ° and ø7 while leaving the rest textual.

The examples below use textual notation throughout.

Extensions vs. Added Tones

The seventh is what turns an upper note into an extension. With a seventh present, a natural ninth, eleventh, or thirteenth continues the tertian stack and is named as an extension. Without the seventh, that same note is an added tone, written with add, and implies no seventh: C9 has a seventh, while Cadd9 does not.

• A natural ninth is 9 when the chord has a seventh, otherwise add9.
• A natural eleventh is 11 when the chord has a seventh, otherwise add11.
• A natural thirteenth is 13 when the chord has a seventh, otherwise 6 (see below).

The lower members of the extensions are optional: a C11 may omit its ninth, and a C13 its ninth and eleventh.

The highest extension present is promoted into the main symbol. Any present lower extension is folded in rather than spelled out separately, while alterations stay explicit. So a dominant thirteenth with a flat ninth and sharp eleventh is C13(♭9,♯11).

Sixth Chords

The seventh is what makes a chord a thirteenth rather than a sixth. With no seventh, a major or minor triad with the sixth degree is a sixth chord, C6 or Cm6; adding a ninth gives the conventional C6/9.

Why not add2 or add4?

Chord symbols say nothing about register, so an added tone’s label never changes with its voicing: a D added to a C triad is the same ninth whether it sits next to the root or an octave above, and an F is the same eleventh either way. There is no need to drop to add2 or add4 just because a note happens to be voiced close to the root.

Register independence rules out voicing-based switching, but it does not by itself favor add9 over add2, or add11 over add4, since each pair ignores register equally. No strict rule settles the choice; add9 and add11 simply prevail as the common convention.

sus2 and sus4 remain distinct because they describe replacement of the third, not merely an added tone.

Alterations

Altered upper extensions are written explicitly: ♭9, ♯9, ♯11, and ♭13. Here ♭ and ♯ mean lowered or raised by a semitone from the natural extension, using whatever accidental the spelling requires; a ♭9 does not necessarily carry a literal flat on the note. When a triad has an altered ninth without the harmonic support for a stacked extension, the symbol can use add♭9 or add♯9.

An altered fifth that defines the base quality normally stays with that quality label. It is usually inline, as in C7♭5, Cmaj7♯5, and Cm♯5. The exception is a bare major triad with a flat five: inline, C♭5 risks reading as a C-flat root rather than a lowered fifth, so the altered fifth is parenthesized as C(♭5). The parenthesized half-diminished spelling Cm7(♭5) is a conventional form kept for familiarity, much like C6/9.

When such a chord also carries other modifiers, the altered fifth joins them in the single trailing group rather than running the accidentals together or stranding a second set of parentheses: a dominant seventh with a flat five and a flat nine is C7(♭5,♭9), and an extended half-diminished chord is Cm9(♭5,♭13), not Cm9(♭5)♭13.

Modifiers are ordered consistently by musical degree: ninths, elevenths, then thirteenths, with alterations placed alongside their degree.

Parentheses

This guide reserves parentheses for grouping and disambiguation. They are one of the least standardized parts of chord symbol notation, used for all sorts of purposes depending on the source. Some teaching styles, such as Berklee-derived materials, parenthesize every tension and alteration as a rule, as in C7(♯11), where we prefer to keep a lone alteration inline as C7♯11.

A symbol carries at most one parenthesized group, placed at the end, so parentheses never appear in the middle of the label or as two separate groups. A group forms only where running the modifiers inline would be ambiguous or hard to read:

• Multiple modifiers are grouped: C7(♭9,♯11).
• Modifiers on suspended seventh chords are grouped rather than run onto the suspension: C7sus4(♭13).
• In textual notation, added tones after the spelled-out aug and dim labels are grouped so the words do not run into add: Cdim(add9) is clearer than Cdimadd9.
• An altered fifth carried in the quality label joins the group when other modifiers are present: C7(♭5,♭9) and Cm9(♭5,♭13).
• Textual minor-major symbols write the major seventh or promoted major extension inside the group, with any other modifiers joining it: Cm(maj7), Cm(maj9), and Cm(maj9,♭13).
• A lone upper-extension modifier after promoted maj11 or maj13 is grouped because the two-digit promoted label is already dense: Cmaj11(♭13) and Cmaj13(♯11).

Where concatenation is already clear, the modifiers stay inline. A single ordinary modifier needs no group: C7♭9, C13♯11, Cmaj9♯11, or Cadd♯9. An added tone reads cleanly inline after a label that already ends in a self-contained mark: the bare root (Cadd9), the fused m (Cmadd11), and the symbolic quality signs + and ° (C+add13).

Textual notation separates grouped modifiers with commas for readability, as in C13(♭9,♯11). Symbolic notation omits them for compactness, writing the same chord as C13(♭9♯11), since the accidentals already mark where each modifier begins.

Omissions

Omission markers such as no5 and omit3 do appear in practice, but this guide avoids them. For the purpose of communicating an identity, they add visual noise without changing which chord is named.

Commonly omitted tones, especially perfect fifths in extended chords, should be understood as part of that chord’s identity rather than turned into a performance instruction. Dropping a structurally important tone, like the third, is a different matter: it weakens the reading instead of simplifying the symbol.

Slash Bass

The slash note names the sounding bass under the chord symbol. It does not change the root, and it does not make the bass note a second chord symbol. A voicing with E in the bass and a C major seventh above it is therefore Cmaj7 / E, not an E-rooted chord unless the notes support that analysis more strongly.

Slash bass also affects which chord tones need to be named explicitly. If an added-tone label would only repeat the bass note, that label is omitted. For example, prefer A♭7 / D♭ over the redundant A♭7(add11) / D♭. Only added tones compress this way; an alteration keeps its label even when the bass supplies that note, so a half-diminished chord with its lowered thirteenth in the bass is still Em7(♭5,♭13) / C, not Em7(♭5) / C.

The same principle keeps slash-bass symbols from overstating stacked extensions. A ninth only earns its place in the main symbol when the chord truly carries it, so a ninth that comes from the bass alone stays in the bass: C7 / D, not C9 / D. The seventh belongs to the quality rather than the extensions, so it never drops out this way and C7 / B♭ stays C7 / B♭.

The slash note names the pitch a player sounds, so it favors a readable spelling. When the bass is a genuine chord tone, its conventional inversion spelling is kept, even where that means a less common letter, as with C♯maj7 / B♯. But when the bass is a color or altered tone, the sounding spelling wins, so a sharp ninth in the bass is A7(♯9) / C, not A7(♯9) / B♯, and double accidentals are avoided.

References

These formatting decisions draw on both historical and modern practice:

• Carl Brandt and Clinton Roemer, Standardized Chord Symbol Notation (1976), an early effort to standardize symbols and remove ambiguity for sight-reading studio musicians.
• Chuck Sher and others, The New Real Book (Sher Music Co., 1988), a practical model of jazz lead-sheet usage, including compact symbols that working musicians are likely to recognize quickly.
• Mark Levine, The Jazz Theory Book (Sher Music Co., 1995), a pedagogical reference for the musical reasoning behind chord qualities, extensions, alterations, and common voicing practice.

Where references or house styles differ, WhatChord favors symbols that are concise, widely recognizable, and clear in a real-time app interface. The goal is not to reproduce any one book’s house style exactly, but to apply the same clarity principles consistently across every displayed chord.

Acknowledgements

This guide was sharpened by the careful reading, edits, and suggestions of u/65TwinReverbRI, whose feedback shaped much of how these conventions are explained.