Extended Chords: Which Tensions Work, and How to Voice Them

A full 13th chord contains seven notes. You will almost never play more than four or five of them.

Which ones you keep is the whole subject. It depends on the quality of the chord underneath, on which tensions sit a half step above a note that is already there, on whether a bass player is covering the root, and on how low in the register you are working. Those decisions are the same whether the chord is a Cmaj9 or an F♯13, which is why they belong on one page rather than being restated on every chord.

Hear the Stack Before You Read About It

Pick a root and a scale below, then open the chord type row and switch Seventh, Ninth, Eleventh and Thirteenth on and off. Each toggle adds one more third to every chord in the table, so you can hold a chord still and listen to a tension arrive and leave.

Two things are worth listening for straight away. Adding the 9th to almost anything makes it sound richer without changing what the chord is. Adding the 11th to a major or dominant chord makes it sound broken. The rest of this page explains why those two are not the same kind of event.

How the Stack Works, and What Gets Dropped

Extensions continue the same process that produced the seventh chord: keep piling thirds on top. Past the 13th the next third lands back on the root, so the 13th is the ceiling of tertian harmony.

The naming convention is where the confusion starts. A chord symbol names the highest tension, and implies everything below it. A 13th chord implies a 9th and an 11th are in the stack. It does not promise they will be played, and usually they are not. The add prefix exists precisely to break that implication: add9 means the 9th and nothing else from the chain, which is why Cadd9 is C E G D with no seventh at all.

So a written symbol describes a ceiling, not a contents list. What actually gets played comes from a fairly reliable order of omission:

The 3rd and 7th are called guide tones because they are the pair that survives every reduction. They are the reason a two-note voicing can still sound like the right chord, and the reason the 5th can leave without anyone noticing.

Avoid Notes: One Rule, Applied Everywhere

An avoid note is a tension sitting a half step above a chord tone. The minor 9th interval between them is the harshest sound in the system, and at close spacing it stops reading as colour and starts reading as a mistake.

That rule accounts for most of the crosses in the table further down, and you can work them out rather than memorising them: name the chord tones, name the tension, and check whether the tension is one semitone above any of them. Two other kinds of conflict fill in the rest. A tension can contradict the chord’s own 3rd, which is why ♯9 is not used on a major chord: it is the ♭3 wearing a different name. And a tension can sit a half step below the 7th, producing the same harsh interval upside down, which is why m7♭5 does not take a natural 13.

The famous case is the natural 11 over a major 3rd. On a C chord the 3rd is E and the 11th is F. A half step. This is why a full C11 with the 3rd in it sounds muddy, why players omit the 3rd instead, and why so many charts that say 11 really mean a suspended chord. It applies to dominant and major chords equally, and it does not apply to minor chords, where the ♭3 (E♭) sits a whole step below the 11th (F) and the two coexist happily. That one interval is the reason m11 chords are everywhere in neo soul and 11 chords with a major 3rd are nowhere.

The ♯11 is the standard escape. Raising the 11th by a semitone moves it a whole step above the 3rd and lands it a tritone above the root, which is the bright Lydian sound rather than a clash. Cmaj7♯11 works where Cmaj11 does not.

There is one large exception to all of this, and it is worth stating plainly: a dominant chord is allowed to clash. Its job is to be unstable and resolve. That is why ♭9, ♯9 and ♭13, all of which would be avoid notes on a tonic chord, are standard colours on a dominant. On a maj7 or a m7 the same intervals just sound wrong, because those chords are meant to be places you can rest.

Which Extensions Suit Which Chord Quality

This is the reference table. Read down for the chord you are playing, across for the tension you are considering.

✓ natural, blends without preparation · ○ altered, a deliberate colour · ✗ avoid, clashes with a chord tone · n/a not used on this quality

A few readings that are easy to miss:

• The dominant row is the permissive one. Every alteration is available because instability is the point. Only the natural 11 is out, and only because of the 3rd.
• The minor rows are the opposite. m7 takes 9, 11 and 13 without any alteration and rejects the altered versions, which is Dorian expressed as a chord.
• The ♭13 on a dominant implies the 5th is gone. ♭13 and ♯5 are the same pitch, a half step above the natural 5th, so you play one or the other.
• 13 is unavailable on m7♭5. The available tensions there are 9 or ♭9, 11 and ♭13, which is Locrian with or without a raised 2nd.
• On 7sus4 the 11 is not a tension at all. The 4th has replaced the 3rd, so it is a chord tone. This is covered in more depth in the guide to suspended chords.

If any of the underlying qualities are unfamiliar, the complete guide to seventh chords covers the four-note chords this table extends, and diatonic chords covers where each quality comes from in a key.

Voicing Principles

Knowing which notes are allowed is half the job. The other half is where you put them.

Guide tones carry the identity

The 3rd and 7th between them establish major, minor or dominant. Everything else is colour or reinforcement. Put the guide tones somewhere in the middle of the voicing, put the tensions above them, and the chord will read clearly even at four notes.

Rootless voicings

Once a bass player is covering the root, playing it again wastes a finger and thickens the bottom of the chord. Rootless voicings drop it and use the space for tensions instead. The two standard shapes, usually credited to Bill Evans, are built either from the 3rd or from the 7th.

Here is a ii-V-I in C using them, and it demonstrates the real reason they are worth learning:

Between Dm9 and G13 exactly one note moves: C falls to B. Two chords that look completely different on paper turn out to be one semitone apart in the hands. That is what rootless voicings buy you, and it is why they became the default for comping. Voice leading this smooth is the subject of the article on chord inversions and voice leading.

Drop voicings

A close voicing stacks every note inside one octave, which gets dense fast. A drop 2 voicing takes the second note from the top and moves it down an octave; drop 3 does the same with the third note from the top. The result spans a wider range and gives every note room to sound. Drop 2 is the standard guitar voicing for seventh and extended chords because it falls naturally under four adjacent strings, and it is the standard way to write a saxophone section.

Spacing in the low register

Low intervals turn to mud, and the effect is physical rather than stylistic. Below roughly the C an octave under middle C, keep the intervals wide: fourths, fifths and sixths. Thirds and seconds down there stop sounding like harmony and start sounding like a rumble. This is the reason a pianist’s left hand tends to play a root and a seventh, or a root and a tenth, and leaves the close tension clusters to the right hand.

Two more habits worth adopting: do not double a tension, because a doubled 9th draws far more attention than a doubled root, and keep the most colourful note on top, because the top voice is the one anybody hears.

The Distinctions That Trip People Up

These three questions account for most of the confusion when reading a chart. Each of them is the same underlying point: whether a seventh is present, and whether the note is a chord tone or a tension.

6 or 13

Same pitch, different job. C6 is C E G A, with no seventh, and the A is a chord tone. C13 is C E G B♭ D A, and the A is a tension sitting on top of a dominant seventh.

The practical consequence: a 6th chord is stable and works as a resting point, while a 13th chord contains a tritone and wants to resolve. If there is no seventh in the chord, it is a 6th, whatever the sound reminds you of.

add9 or 9

Cadd9 is C E G D. C9 is C E G B♭ D. The difference is the ♭7.

add9 is the instruction to take the 9th without the chain below it, which is why the chord stays bright and open and turns up constantly in folk, pop and rock guitar. C9 with its seventh is a dominant chord and carries dominant function, which is why it belongs to funk and blues. Same added note, completely different harmonic behaviour.

C6/9 is the third member of this family: C E G A D, with a 6th and a 9th and no seventh at all. It is a tonic chord with two tensions and no avoid note anywhere in it, which is why it is such a common final chord.

sus4 or 11

Csus4 is C F G. The 4th has replaced the 3rd, so there is no clash to manage.

C11 is written as though the 3rd were still there, but in practice it is voiced C G B♭ D F, with the 3rd omitted for exactly the reason described in the avoid note section. Once the 3rd is gone, what remains is a 7sus4 chord with a 9th on top. This is why experienced arrangers tend to write G7sus or G7sus(9) rather than G11: the sus symbol describes what will actually be played, and the 11 symbol describes a chord nobody voices literally.

Cm11 is the exception that proves it. C E♭ G B♭ D F is the only extension chord in common use whose full seven note stack is playable as written, with nothing omitted, and that is entirely down to the ♭3.

Where to Take This Next

The fastest way to internalise any of this is to stop reading and start toggling. Take a chord you already play, add the 9th, and listen. Add the 11th and listen to the difference between doing that over a minor chord and over a major one. The clash is far more convincing heard than described.

From here, seventh chords covers the four note chords underneath all of this, suspended chords covers the sus family the 11 keeps turning into, and secondary dominants and borrowed chords covers what to do with an altered dominant once you have voiced one.

Every Extended Chord in Every Key

Each chord type below links to a dedicated page for all twelve roots, with the notes, the piano shape, the guitar voicings, the inversions and the keys the chord belongs to.

Add9: C, C♯, D, E♭, E, F, F♯, G, A♭, A, B♭, B

Dominant 9th: C, C♯, D, E♭, E, F, F♯, G, A♭, A, B♭, B

Major 9th: C, C♯, D, E♭, E, F, F♯, G, A♭, A, B♭, B

Minor 9th: C, C♯, D, E♭, E, F, F♯, G, A♭, A, B♭, B

Dominant 11th: C, C♯, D, E♭, E, F, F♯, G, A♭, A, B♭, B

Dominant 13th: C, C♯, D, E♭, E, F, F♯, G, A♭, A, B♭, B

Six-nine: C, C♯, D, E♭, E, F, F♯, G, A♭, A, B♭, B