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The problem it solves
The third is the note that decides whether a chord is major or minor. If you replace it with the second or the fourth, the chord is left "suspended": neither bright nor dark, just open. Knowing how to do this gives you a colour that is very useful in pop, rock and folk.
Detailed theory
Key idea
A suspended chord has no third: the sus2 swaps it for the second (1-2-5) and the sus4 for the fourth (1-4-5).
The suspended note usually resolves to the third: in the sus4 the fourth steps down a semitone to the third; in the sus2 the second steps up a tone to the third.
Understand it
A normal triad has the root, the third and the fifth. The third is the piece that chooses the colour: if it is major the chord sounds major, if it is minor it sounds minor. A suspended chord removes that third and replaces it with a neighbouring note, so the colour is left in suspense.
There are two options. The sus4 puts the fourth where the third was: in C, Csus4 = C-F-G (1-4-5). The sus2 puts the second: Csus2 = C-D-G (1-2-5). In both cases the fifth (G) stays and the root (C) too; only the middle note changes.
Because there is no third, the ear cannot tell whether the chord is major or minor, which is why it sounds open, bright and a little expectant. That "needs to resolve" feeling is what gives the suspension its name.
The natural resolution is to return the third to its place. In the sus4 the fourth steps down a semitone to the third (in C, the F drops to E and Csus4 becomes C major). In the sus2 the second steps up a tone to the third (the D rises to E). That is why you often find sus4 → chord right before an important arrival.
Think of it as a held breath: the suspended chord is the air kept in, and resolving to the third is letting it out. While the third has not arrived, the chord stays floating; when it arrives, everything settles.
Staff & keyboard
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The resolution of the sus4: the F (fourth) steps down a semitone to E (third), and Csus4 (C-F-G) becomes C major (C-E-G).
How to recognise it
How it's written
In the chord symbol, sus4 (or simply sus) means the fourth takes the place of the third; sus2 means the second does. Csus4 = C-F-G; Csus2 = C-D-G. If there is no number after sus, sus4 is understood.
How it feels
Play Csus4 (C-F-G) and then C major (C-E-G): you will hear the open chord close as the F steps down to E. That small one-semitone move is the characteristic sound of the suspension resolving.
Common mistake
Thinking a suspended chord is major or minor: it is precisely neither, because it is missing the third that decides the colour.
Confusing the sus2 with an add9: the sus2 replaces the third (it is gone), whereas the add9 keeps it and adds the ninth on top.
Try it
On the keyboard, play C-F-G (Csus4) and then drop the F to E to get C major: you have just resolved the suspension.
Now try C-D-G (Csus2) and raise the D to E: the second resolves to the third and you are back at C major.
On the instrument
Staff & keyboard
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Csus4 = C-F-G. There is no third: the fourth (F) takes its place and leaves the chord open, with no major or minor colour.
Where it's used
- Creating tension and release
- Placing a sus4 just before a chord so the fourth resolves to the third and marks an arrival.
- Giving an open colour
- Replacing the third with the second or the fourth for a wide, undefined chord, very common in pop, rock and folk.
- Telling sus2 and sus4 apart by ear
- Recognising that neither is major or minor and identifying whether the suspended note resolves up (sus2) or down (sus4).
Examples
Chord progression
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Csus4 → C major: the fourth (F) resolves down to the third (E). Listen to the open chord close.
Chord progression
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Csus2 → C major: the second (D) resolves up to the third (E). The same suspension game, now from below.
Exercises
Play suspended chords (sus2/sus4)
Play the suspended chord (sus2 or sus4) shown, on any root.
Complete 6 attempts · 70% accuracy to pass
Mini test
Check that you've got it.
0/7 answeredQuestion 1/7
What replaces the third in a suspended chord?