Sus2 vs Sus4 Chords (and Add9): What's the Difference?

Sus2 and sus4 chords both drop the third and put another note in its place: a sus2 uses the 2nd (Csus2 is C D G) and a sus4 uses the 4th (Csus4 is C F G). With no third, neither chord is major or minor, so sus2 sounds open and floaty while sus4 sounds tense and wants to fall back to the plain chord. Add9 is different: it keeps the third and adds the 2nd an octave up (Cadd9 is C E G D), so it stays a major chord.

What is a sus2 chord?

A regular major or minor chord is a triad: a root, a third and a fifth. The third decides the mood. C E G is major because E sits four semitones above C. C Eb G is minor because Eb sits three semitones above C.

A sus2 chord drops the third and uses the note a whole step above the root instead. Csus2 is C D G, Dsus2 is D E A, and Asus2 is A B E. As a recipe in semitones it is 0, 2, 7: the root, two up, seven up.

Because that D could step up to E (major) or to Eb (minor), the chord never commits either way. It sounds like a bare fifth with a little shimmer in it, and it sits happily under a melody that has not decided whether it is happy or sad.

“Sus” is short for suspended chord. The name comes from older counterpoint, where a note from one chord is held over (suspended) into the next chord and then steps onto a chord tone. Pop music kept the sound and mostly dropped the rule that it has to step anywhere.

On guitar, the open D chord shows it best. The usual shape, xx0232, plays D A D F#. Lift your finger off the high E string (xx0230) and the F# becomes an open E: that is Dsus2. The same trick works on A: x02220 is A major, x02200 is Asus2.

What is a sus4 chord?

A sus4 chord replaces the third with the note a perfect fourth above the root, five semitones up. Csus4 is C F G, Gsus4 is G C D, and Dsus4 is D G A. The recipe is 0, 5, 7. When a chart writes plain “sus” with no number, it means sus4, so Gsus is G C D.

In a major chord, the 4th sits only a half step above the third (F sits right above E in C). That half step is where the tension comes from. Your ear hears the F as a note that belongs a half step lower, so Csus4 sounds like a question, and C is the answer. Classical theory calls this move a 4-3 suspension, because the 4th falls to the 3rd, and pop songs use it for the same pull.

Back to the D shape on guitar: xx0233 puts a G on the high E string, which makes Dsus4. For A, x02230 is Asus4. Put the three D shapes together (xx0230, xx0232, xx0233) and you have sus2, major and sus4 on a single string, which is why guitarists wiggle between them to make one chord move.

Sus2 vs sus4 in thirty seconds on a keyboard

You can hear all three in thirty seconds on any piano or keyboard app. Hold C4 (middle C) and G4 with two fingers. Add D4 with a third finger: Csus2. Swap the D for E4: C major. Swap the E for F4: Csus4. Then go back to E4. Play D, E, F, E slowly and listen to the middle note.

The D sounds calm and a little hollow. The E sounds settled. The F leans, and the moment you move it down to E you feel the chord sit down. That lean is the whole difference in one note.

Csus2 and Gsus4 are the same three notes. Stack C D G starting from G and you get G C D. Every sus2 chord is a sus4 chord on the note a fifth higher, rearranged, and the bass note decides which one you hear. With C in the bass it floats as Csus2. With G in the bass it sounds like Gsus4 waiting to become G.

In Gelato Synth, the comparison is one tap away. Chords mode (part of the one-time $4.99 purchase) has a chord-type row that switches all eight pads at once, with Triad, Sus2 and Sus4 among its seven choices, so you can play the V pad as a triad, then as a sus2, then as a sus4, and hear the third come and go.

When to use sus chords (and what they resolve to)

In C major, ten sus chords use only white keys, so any of them fits a song in that key:

Five moves cover most of what sus chords do in songs:

• Sus4 to major on the same root. Gsus4 to G, with the C falling a half step to B. It works best on the V chord right before home: in C major, play F, Gsus4, G, C. The sus4 holds off the G by a beat or a bar, so the final C lands harder. Play the plain F, G, C on the free online chord player first, then play it on a keyboard with Gsus4 (G C D) slipped in before the G (G B D), and compare.
• Sus4 to minor. Asus4 to Am also works: the D steps down a whole step to C. It is a softer landing than the half-step fall.
• Sus2 up to the third. Csus2 can rise to C (D up to E) or to Cm (D up to Eb). Use it when you want the listener to find out late whether the chord is major or minor.
• Sus2 left alone. Plenty of pop songs never resolve their sus2 chords. A loop of Csus2, Asus2, Fsus2 and Gsus2 is I, vi, IV, V in C major with every third removed, so it sounds wide and unsettled for as long as you like. There are more progressions in this spirit in dreamy chord progressions.
• The 7sus4. G7sus4 (G C D F) keeps the F, the 7th that pulls down to E when the chord moves to C, and leaves out the B. It is a jazz staple, often voiced as F/G: an F triad over a G bass note, which is G9sus4 without its fifth.

One practical check before you drop a sus4 into a song: look at the melody. If the singer holds E over Csus4, the E and the F sit a half step apart and rub. Either let the melody move or play the plain C under that note. A sus2 is more forgiving, because a melody on E just turns it into a Cadd9.

Add9 vs sus2: does the chord keep its third?

Cadd9 is C E G D. Csus2 is C D G. The only difference is the E. With the E, you hear a clear major chord with some sparkle on top. Without it, the chord is open and undecided. An add9 chord adds the D; a sus2 swaps the E for it.

The 9 and the 2 are the same note letter an octave apart: a 2nd plus an octave is a 9th. Charts write add9 when the D sits above the chord and there is no 7th in it. You will also see Cadd2, which places the D inside the chord, right between C and E (C D E G), for a tighter, crunchier sound. C9, with no “add”, always brings the Bb along, and that Bb changes the flavor more than the D does.

Gelato Chord spreads this range across one control, its color wheel (labeled VOICING in the app). Pull it down from Home toward Sus and the chord you are holding opens out toward a sus sound. Push it up and extensions such as the 9th and 7th join in. The bass note stays where it is the whole time, so the wheel only colors the chord you are already on.

On guitar, take an open C (x32010) and move the finger on the B string from the 1st fret to the 3rd: x32030 plays C E G D E, a Cadd9. On piano, play C E G with your right hand and put the D on top, above the G.

Pick add9 when the chord has to stay clearly major or minor, for example under a vocal that sings the third, but you want a little air in it. Pick sus2 when you want to leave the major or minor question open.