Sus chords

”Sus” stands for suspension and what happens in these chords are that the third (the second note) are being replaced with either a major second or a perfect four. Then it is replaced with a major second the chord name is sus2, and then it is replaced with a perfect four the chord name is sus4. There are also extended suspended chords.

See diagrams of sus chords:

C sus D sus E sus F sus G sus A sus B sus

C7 sus D7 sus E7 sus F7 sus G7 sus A7 sus B7 sus

Theory

We can compare a C major chord with Csus2 and Csus4:

C: C – E – G
C chord

Csus2: C – D – G
csus2 chord

Csus4: C – F – G
csus4 chord

Formulas

The formulas are 1 - 2 - 5 (sus2) and 1 - 4 - 5 (sus4).

Other sus chords

Beside the common sus2 and sus4 chords there are more categories. A seventh or a ninth chord, for example, could be suspended.

Let us compare a C7 chord with C7 sus chords:

C7: C – E – G – Bb
C7sus2: C – D – G – Bb
C7sus4: C – F – G – Bb

Finally, let us compare a C9 chord with a C9sus4 chord:

C9: C – E – G – Bb – D
C9sus4: C – F – G – Bb – D

Alternative chord names

Besides the standard sus4/sus2 names, the annotation C4, D4, E4 and so forth can occur and often together with C3, D3, E3 and so forth (meaning a sequence sus to major).