The basics of chord symbols

Seven letters, and why they start on A

A to G, and then round again. The obvious question, which most people ask once and then stop asking, is why the ladder starts on A when the first scale anybody is taught starts on C.

The answer is that the letters are older than the habit. Naming pitches with letters goes back a long way, and the repeating A to G scheme is described in medieval treatises on the monochord, around the year 1000. In that lettering the seven letters with no sharps and no flats are A, B, C, D, E, F, G, and the note the lettering starts from is A.

Play those seven in order on white keys, A up to A, and listen. It is not a major scale. It is what we now call A natural minor. The letters were fixed on that set of notes before the major scale became the default way European music thought about itself, and once they were in the books nobody renamed them.

Teaching, meanwhile, settled on C, for the simplest possible reason: C D E F G A B is the major scale that needs no sharps and no flats. All white keys, nothing to explain.

And the two are the same seven notes. That is not a coincidence to be memorised. It is the first useful fact here, and the section on modes at the end of this article is nothing more than that observation taken seriously.

One warning while we are on letters: they are not even universal. German language practice writes B for B flat and H for B natural, so a German edition may print H7 where an American one prints B7.

The third: major is the default

A letter on its own means a major triad. C is C, E, G: the root, a major third above it, a perfect fifth above the root.

Minor has to be asked for, and there are four spellings in circulation. Cm, Cmin, Cmi and C- all mean C, E flat, G. The dash is Real Book house style and very common among jazz players; printed music and software mostly use the m, partly because a dash is easy to mistake for a hyphen and impossible to search for.

Why is major the default? The reason usually given, and the only one that makes the rest of the system coherent, is economy: the shortest symbol goes to the commonest chord. In the music this notation grew up serving, the plain major triad is the chord you write most often by a wide margin, so it got the shortest symbol available, which is nothing at all.

Hold on to that sentence. It is about to explain something that looks like a contradiction.

The seventh: minor is the default

Add a seventh and the rule turns over.

C7 does not mean C major with a major seventh. It means C, E, G, B flat. The third is still major. The seventh is minor. If you want the major seventh you have to ask for it, and the mark that asks for it is a triangle: C∆, or C∆7 when the seven is spelled out. That is what Chord Analyser draws, and what a jazz chart is most likely to show you. You will also meet Cmaj7, CM7 and Cma7 in print, and they are the same chord. Chord Analyser accepts the spelled-out Maj7 when you type it and simply draws the triangle back at you.

Read that twice. It is the single thing that confuses beginners most, and it confuses them for a good reason: it looks as though the notation contradicts itself. Major is the default for the third. Minor is the default for the seventh.

It is the same rule both times. The shortest symbol goes to the commonest chord. And the commonest four note chord in this repertoire, by a distance, is the one with a major third and a minor seventh: the dominant seventh, the chord that pulls back to the tonic and announces the key while it does it. Nothing else was ever in contention. So it got the bare number.

You can watch it happen inside one scale. Harmonise C major in sevenths and you get C∆, Dm7, Em7, F∆, G7, Am7, Bø7. Exactly one of those seven has a major third and a minor seventh, and it is the fifth degree. It is also the only chord in the key whose sound tells you which key you are in. Of course it got the short name.

The four combinations, once and for all

Two independent questions, third and seventh, two answers each. Four chords. Learn this square and most of the confusion goes away.

The way to make it stick is to stop reading the symbol as one word. Read it as two questions. The letter answers the third, and defaults to major. The number answers the seventh, and defaults to minor. Neither default is arbitrary, and both come from the same place: the commonest thing needs no mark.

The rest of the vocabulary

Sixths

C6 is C, E, G, A. A sixth added to the triad, and no seventh at all.

Cm6 catches people out: it is C, E flat, G, A. A minor triad with a major sixth. The sixth in a 6 chord is major whatever the third is doing. If you really want an A flat over a C you are describing something else, and you would write it as an inversion of A flat, or as C(♭13), not as a sixth.

C6/9 is C, E, G, A, D. That slash is not a bass note: it is the one common symbol where a slash means "and". Software that reads chord symbols has to special-case it, and Chord Analyser does, by only treating a slash as a bass slash when what follows it starts with a letter from A to G.

Ninths, elevenths, thirteenths

A number above 7 in the body of the symbol does two jobs at once: it puts that note in the chord, and it implies everything below it down to the seventh.

• C9 is C, E, G, B♭, D. The 9 brought the 7 with it.
• C11 is, strictly, C, E, G, B♭, D, F. In practice the third gets dropped, because F sits a semitone above E and the pair sounds like a mistake rather than a colour. Take the E out and C11 is the same set of notes as C9sus4.
• C13 is C, E, G, B♭, D, A. In practice the fifth goes and so does the eleventh; C, E, B♭, D, A is what somebody actually plays.

Here is where a house style rule earns its keep. A number in the body of the symbol implies the ones below it, while an alteration in brackets attached to a 7 implies only the 7. So C13 has a ninth in it and C7(13) does not. Chord Analyser's dictionary keeps those two apart as genuinely different chords, which is a fair sign the distinction is real and not pedantry.

The eleventh needs one more rule. Over a minor chord it is natural: Cm11 has an F in it and nothing complains, because the third is E flat and there is a whole tone between them. Over a major or dominant chord it is normally raised: you write C7(♯11), not C7(11). The same split shows up in Chord Analyser's dictionary, where the natural eleventh lives on minor chords and the sharp eleventh on dominant ones.

Added notes

Cadd9 is C, E, G, D: a ninth added to a plain triad, with no seventh. The word "add" is doing exactly one job, which is to cancel the implication that a 9 drags a 7 along behind it. Chord Analyser writes this chord C(9) and lists Cadd9 as the same thing. Both spellings are in wide use, and some pop and worship charts write it C2.

Suspensions

Csus4 is C, F, G. The fourth does not join the third, it replaces it, which is why a sus chord has no quality: there is no third left to be major or minor. Csus2 is C, D, G.

Two cautions. Some charts write sus on its own and mean sus4. And a suspension does not have to resolve, whatever the word suggests: a great deal of pop music simply leaves it hanging, and C7sus4 (C, F, G, B♭) is a staple of gospel and soul that wants no resolution at all.

Diminished, and the trap inside it

Three different chords get called "diminished" out loud and they are not the same chord.

• Co, a lowercase letter o, which is how Chord Analyser draws it. Also written Cdim, C° or Cm(♭5). C, E♭, G♭: a minor third and a flattened fifth. Three notes.
• Co7, also written Cdim7 or C°7: C, E♭, G♭, A. Three minor thirds stacked, which is why the top note is strictly a B double flat and played as an A. Add the minor third from that A back up to C and the chord has cut the octave into four equal pieces, which is why there are only three distinct chords of this kind in all of music.
• Cø7, an o with a stroke through it, called half diminished. Also written Cm7♭5 or Cm7(♭5), which is the commoner spelling in print. C, E♭, G♭, B♭. One note away from Co7, and it is the note that matters, because this chord is the ii of a minor key and behaves nothing like the other one.

Notice the shape of the problem. On the page o7 and ø7 differ by one stroke, and in the chord they differ by one note, and out loud both get called "dim". So when you are writing by hand for somebody else and there is any room for doubt, write m7♭5 in full: it costs three characters and it cannot be misread.

Augmented

C+ is C, E, G♯: a major third and a raised fifth. The plus is the usual mark and the one Chord Analyser draws; you will also see Caug.

Watch the plus sign, because it does two jobs. On its own after the letter it means the augmented triad. Next to a number, especially in an older chart, it means "raise this", so C7+9 is what we would now write C7(♯9) and C7+5 is C7(♯5). A minus sign in the same position means "lower this", which is why you also meet C7-9 for C7(♭9).

Alterations, in brackets

When a note is altered away from what the symbol would otherwise imply, it goes in brackets after it. C7(♭9) is C, E, G, B♭, D♭.

Several alterations go inside one pair of brackets, in ascending order of the degree they alter: C7(♭5,♭9), not C7(♭9)(♭5) and not C7(♭9,♭5). Chord Analyser orders them fifth, then ninth, then eleventh, then thirteenth, which is the usual order in print.

One note on typography, because it explains a real ambiguity. Set properly, the root is at full size and the alteration is small and raised, so nothing is in doubt. Typed as plain text, C♯11 could be a C sharp chord with an eleventh, or a C chord with a sharp eleventh. This is why chord symbols get typeset rather than typed, and why a chart written in a text editor needs its brackets more than a printed one does.

Slash chords

A slash followed by a letter names the bass note and changes nothing else. C/E is a C major triad with E at the bottom. C/G is one with G at the bottom.

• The bass note is usually a note of the chord and does not have to be. Dm7/G is a D minor seventh over a G that is not in it, which is a perfectly normal way of writing a chord that would otherwise take a sentence.
• The slash is addressed to the bass player. Everybody else reads the part in front of it and carries on.
• Whether to write one at all is an editorial judgement, not a fact. Chord Analyser has two settings for exactly this: one marks every inversion with a slash, and the default only writes one when the bass sits a long way below the chord or is foreign to it.

Two marks that are not chords

A bar filled with oblique strokes means "keep playing, on the chord that is already sounding". The strokes count beats, not chords. And N.C. means no chord: stop playing harmony, usually because something else is exposed.

How to read any symbol, in order

Five steps, always in this order. Once it is a habit you will do it faster than you can read this list.

1. The root. The letter, plus any sharp or flat immediately touching it. In C♯m7 the root is C sharp; that accidental belongs to the letter, not to the quality.
2. The third. m, min, mi or - means minor. o, dim or a circle means minor and a flat fifth as well. sus means there is no third at all. Nothing at all means major.
3. The seventh. A bare 7, 9, 11 or 13 means the seventh is minor. A triangle, ∆, means it is major, and so do the spelled-out maj7, M7 and ma7. A 6 means a sixth instead of a seventh. add means no seventh at all. The one exception is a diminished seventh, o7 or dim7, whose seventh is diminished, a semitone below the minor seventh.
4. Everything in brackets alters a note that steps 2 and 3 have already put in the chord. It never adds a new degree out of nowhere.
5. The slash, if there is one, names the bass note and changes nothing else.

Three worked examples, to see the steps run:

• E♭∆: root E flat. No minor marker, so a major third, G. Fifth, B flat. The triangle, so a major seventh, D. Four notes: E♭ G B♭ D.
• F♯m7♭5, the same chord Chord Analyser would draw as F♯ø7: root F sharp. m, so a minor third, A. The ♭5 flattens the fifth to C. Bare 7, so a minor seventh, E. Four notes: F♯ A C E.
• G7(♭9)/D: root G, major third B, fifth D, minor seventh F, and the bracket flattens the ninth to A flat. The slash puts D in the bass. G B D F A♭, with D at the bottom.

The same chords, spelled by different people

There is no standards body for any of this. Every column below is current somewhere, in print, today. When two charts disagree, you have not found two chords, you have found two copyists.

The first entry in each row above is the one Chord Analyser draws, which makes it a useful second opinion when a symbol looks ambiguous. Its house style, in full: minor is m, with min as an alternative and never a dash. The major seventh is the triangle ∆, so Maj7 becomes ∆ and Maj9 becomes ∆9. The diminished is a lowercase o, not a degree sign. The half diminished is ø. The augmented is +. Alterations use the musical signs ♭ and ♯, not the letter b and the hash.

Worth being clear about what that is and is not. It is a drawing convention, not a restriction on what you can type: the app takes Maj7 from you happily and hands back ∆. And it is one program's set of choices, all defensible, none of them the rule. Open a Real Book and you will meet the other family within a page.

Scales, degrees and modes

Now the part that connects symbols to the notes you actually play.

Take the major scale and build a chord on each of its seven notes, using only notes from that scale. In C major, you get this. The Roman numerals are the analysis notation from part 1 of this series; they are here because a chart will sometimes use them and because they make the pattern visible.

A few things fall out of that table that are worth saying out loud.

Only one degree gives you a bare 7, and it is the fifth. That is the argument from earlier, now visible. Only one chord in the key has a major third and a minor seventh, and it is the chord that tells you what the key is.

The seventh degree looks strange on its own and is usually not on its own. Bø7 is B, D, F, A, which is a G9 with its root taken away. That is why it so often behaves like the dominant rather than like a chord of its own.

And the three shapes repeat: ∆ on I and IV, m7 on ii, iii and vi, a lone 7 on V. If a chart in C major hands you an Fm7 or an A7, those are not in the key, and that is information: something is being borrowed, or the tune has moved.

What a mode is

A mode is not a new set of notes. It is the same set read from a different starting point.

Play white keys from D up to D. You have played the notes of C major and nothing else. But because you started and finished on D, D sounds like home, and the intervals measured from that home are different: the third above D is F, which is a minor third. So the mode has a minor flavour while using not one note outside C major. That mode is D Dorian, and its chord is Dm7, which is the ii of C major. Same seven notes, different centre of gravity.

The other six work the same way, and the names in the table above are just the seven places you can start: Ionian on C, Dorian on D, Phrygian on E, Lydian on F, Mixolydian on G, Aeolian on A, Locrian on B. Seven names, one set of notes.

What it means when you are looking at a chart

There are two cases, and they are not equally interesting.

Case one: the chord belongs to the key. You are in C major and the bar says Dm7. D Dorian and C major contain exactly the same seven notes, so there is nothing new to learn. Play the notes of the key, and know that D is home for the moment. The mode name is a description of where you are standing, not an extra thing to memorise. This is worth being blunt about: a lot of people spend months learning seven mode fingerings that are one fingering.

Case two: the chord does not belong to the key. A bar of B♭7 in a tune in C major is outside the key, because B flat and A flat are not in it. Now you genuinely need a set of notes chosen for that chord alone, and now naming the mode is doing real work, because the name is what tells you which notes. This is where thinking in chord scales earns its keep, and not much before.

Two honest caveats

That table is the major scale only. Minor keys are messier, because three minor scales are in common use. In A minor the fifth degree is Em7 if you take the notes straight out of the natural minor scale, and E7 if you raise the seventh degree of the scale to G sharp, which is what nearly every piece of music in A minor actually does, because that G sharp is the note that makes the chord pull home. Harmonic and melodic minor change several other degrees too. There is no one page version, and anybody offering you one is simplifying.

Chord scale thinking is a method, not the truth. It is strongly associated with George Russell's Lydian Chromatic Concept of 1953 and with the Berklee teaching tradition that followed, and it is genuinely useful. It is also not how everyone thinks. Plenty of excellent improvisers work from guide tones, from the two or three notes that change between one chord and the next, and never name a mode at all.