Sus chords are particularly common in pop music. Sus is an abbreviation of ´suspension ´. In a theoretical aspect what’s happening with the chord when you add sus to it are that the third note in the scale (i.e. the second note in the chord) is flattened or raised one step. There are sus2 and sus4 chords. In the first case, the note is flattened and in the second case it’s raised.
The C chord consists of the notes C, E and G. In a Csus2 chord the E note changes to D and in a Csus4 the E note subsequently changes to F. One more thing: sometimes the name of the chord is written as "Csus" without any 2 or 4. In this case, you should treat it as a Csus4.
Common sus chords
How to use the sus chords
As always in music, there’re many ways to tackle things. A very common procedure, however, concerning these chords are to alternate between the original chord and the sus chord of the same root note. For example: D to Dsus and back to D.
A specific figure is: D – Dsus4 – D – Dsus2 – D.
(This one can be found in the intro of Bob Dylan’s “Mr. Tambourine Man”.)
Another figure is: A – Asus2 – A – Asus4 – A – Asus2 – A.
(This riff can be heard in the Tom Petty song “Feel a Whole Lot Better”.)
A chord progression you can try out to get a sense of how the sus chords can function together with its original chord is: E – Esus4 – E – D – Dsus4 – D – A – Asus4 – A – E.
So when using sus chords you are normally not substituting the major chord with it, but instead using it together with a major chord. So instead for a progression like Dsus4 - A - G, it will often sound better with a progression like D - Dsus4 - A - G. The same case is that instead for G - A - Dsus4 it’s more common to play like G - A - D - Dsus4 - D.
One important thing to think of when you are playing these kinds of chord progressions is to avoid lifting all your fingers when the chord changes (from major to sus and vice versa). If you are using the correct fingerings you just have to lift one finger or add a finger depending on the chord (see easy chords for diagrams).