The voicing family

Chord extensions on guitar: which note do you drop?

A seventh chord already takes all four fingers. To make it a ninth, an eleventh, or a thirteenth, something has to give — and on guitar the note you give up is the whole trick. Keep the third and seventh, hand the root to the bass, and the color tone takes the empty string.

Seven notes, four strings

Extensions are the notes stacked above the seventh: the ninth, the eleventh, the thirteenth. Keep stacking thirds past the seventh and you reach them — a full thirteenth chord names all seven notes of the scale at once. A pianist can grab six of them under two hands. You have four strings worth of chord and a fourth finger that has already run out. So a chord symbol like G13 is never an instruction to play seven notes. It is an instruction to choose four.

The choice is not free, and it is not yours to improvise. Line the seven notes up and the order they leave in is fixed:

The third and the seventh stay because they are the guide tones — the pair that says what kind of chord this is, the ones a shell voicing is built on. The root goes first: in a band the bass has it, and up here it is hard to reach anyway. The fifth goes next; it never told you much. The eleventh has its own problem, which we will come back to. What is left is two guide tones and two open strings — and those two strings are exactly where the color lives.

The ii–V–I, one color each

Here is the same ii–V–I in C this family keeps returning to, now with a color tone added to every chord. Look at the D and G strings: the guide tones have not moved a fret from the guide-tones lesson. All the new sound is on the B and e strings, where the root and fifth used to be. These are rootless voicings — the bass, real or imagined, supplies the note they leave out.

The voicings you hear are the app’s own sampled guitar — from the MuseScore General sound library, used under the MIT license.

Hear the color go on

Play the plain drop-2 ii–V–I first, then the extended one. The progression is the same and the guide tones do the same work — the seventh of each chord still falls a half step to the third of the next, the voice-leading seesaw that drives the whole family. What extensions add rides above that: a ninth and a thirteenth in place of a plain chord’s root and fifth.

Nothing about the progression got harder to follow — it got richer. That is the point of extensions on guitar: they are not new chords, they are the chords you already comp, with the two least useful notes swapped for the two most flavorful ones.

One thing a solo guitar hides, though: these extended shapes are rootless. The bass — real or imagined — supplies the root they leave out, and on their own the ear can feel that root missing. So here is that bass made real, playing the roots D, G, and C under the same two progressions:

With the root handed off, nothing the guitar plays is spent holding down the bottom. Every string carries a third, a seventh, or a color tone, and the ninths and thirteenths ring out over a foundation instead of floating free. That is the sound these voicings were built for — a bass under the roots and the guitar free to be all flavour — and it is the band the app’s Play-Along puts beneath your comping.

The dominant takes the alterations

The V chord is where jazz reaches for tension, because tension is exactly what a dominant is for — it wants to resolve, and a sharpened color makes it want to resolve harder. The swaps work the same way; you just aim the color tone at an altered note instead of a natural one. Pull the 9th down a half step and G13 becomes G13♭9 — the same grip with one finger moved back a fret, and a darker, more urgent pull into Cmaj9:

Raise a color instead of lowering it and you get the other altered tones — a ♯9, or the ♯11 that jazz loves on a major chord. Which brings us back to the plain 11th, the one note you never saw added above: a natural 11th sits one half step above the major third and grinds against it, so guitarists raise it to a ♯11 or leave it out entirely. That is why 9ths and 13ths dress up these chords freely while the 11th keeps to itself — the same “does it clash with a guide tone?” test that decides every note in the voicing.

Where Drop2 comes in

Every extension here is a drop-2 shape with one or two notes re-pointed at color — so the shapes to own first are the plain ones, and that is what the Drop2 app drills today. Learn and Train cover every inversion of maj7, 7, m7, m7♭5, dim7, and mMaj7 across all three string sets, free with no time limit, with the app listening through your phone’s microphone and grading each grip by ear. Extended voicings are a coming addition, one step up from the drop-2 shapes the app teaches now. Get the four-note frames under your fingers here; the ninths and thirteenths are two notes away.