Beyond the triad

#music/voicings · Note 5 of 9 · part of Guitar

A triad is three notes (Chords). Everything here is what happens when you take one away, or add one on top. Two different operations, and the names tell you which — once you know the rule.

sus replaces the third. add keeps it.

That single sentence is the whole distinction, and it is the thing most chord charts never say out loud.

Suspended chords — the third removed

The third is the note that decides major or minor (Chords). Take it out and the chord becomes neither. That ambiguity is the entire point.

Why "suspended"

Originally a suspension was a rhythmic device: a note held over from the previous chord, clashing with the new one, then falling to the third a beat later. The tension existed to be resolved.

Modern usage keeps the sound and drops the obligation. A sus chord can simply sit there. But the pull is still audible — a sus4 genuinely wants to fall to the major third, and that wanting is why the chord is useful.

Dsus2 and Dsus4 on the guitar

D major is the ideal demonstration, because the third sits on the top string where one finger controls it:

        6 5 4 3 2 1
D       x x 0 2 3 2      D  A  D  F♯
  ← the F♯ is the third
Dsus2   x x 0 2 3 0      D  A  D  E
  ← lift the middle finger
Dsus4   x x 0 2 3 3      D  A  D  G
  ← add the little finger

One finger, three chords. Play D → Dsus4 → D → Dsus2 → D slowly and you can hear the third leave and come back. It is the most efficient theory lesson available on the instrument.

The same works on A:

A       x 0 2 2 2 0
Asus2   x 0 2 2 0 0
Asus4   x 0 2 2 3 0

And on E, where only sus4 is comfortable: Esus4 0 2 2 2 0 0.

Csus2 is awkward in open position — x 3 0 0 1 3 — which is part of why guitarists reach for Cadd9 instead.

Added chords — the third stays

An add chord keeps all three triad notes and puts one more on top.

Cadd9 = C · E · G · D

The D is the 9th. It is the same pitch class as the 2nd — Re — just an octave higher.

So Csus2 is ambiguous and hollow; Cadd9 is unmistakably major, just shimmering. Same two pitches involved, completely different character, because one chord still has its third.

Why 9 and not 2

The numbering is not decorative. Chord degrees past 7 mean the chord reaches past an octave:

1  2  3  4  5  6  7  8  9  10  11  12  13
Sa Re Ga Ma Pa Dha Ni Sa′ Re′ Ga′ Ma′ Pa′

• sus2 uses "2" because the note sits inside the triad, standing in for the third.
• add9 uses "9" because the note sits above the triad, an octave up.

And one more trap: a plain C9 is not Cadd9. Numbers of 9 and above normally imply the 7th is in there too — C9 is C E G B♭ D. The word add exists precisely to say "the ninth, and no seventh".

Cadd9 on the guitar

        6 5 4 3 2 1
C       x 3 2 0 1 0
Cadd9   x 3 2 0 3 0
  ← 2nd string moves from fret 1 to fret 3

Guitarists use it constantly, and for a physical reason rather than a musical one. Compare:

G       3 2 0 0 0 3
Cadd9   x 3 2 0 3 0
D/F♯    2 0 0 2 3 2
Em7     0 2 2 0 3 0

Your third and little fingers can stay planted on the top two strings across all four. The progression plays itself, and the ringing open G and high E thread through every chord. That is why so much acoustic music lives in this shape family.

The rest, briefly

add11 rarely works on guitar, because the 4th sits a semitone above the 3rd and the two grind. Which is a decent illustration of the whole idea: the third is the most opinionated note in the chord, and every one of these names is really a statement about what you did to it.

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