C Suspended 4th
sus4
0 - 5 - 7Root + perfect 4th + perfect 5th
About C Suspended 4th
Csus4 replaces the E of a C major chord with an F — C, F, G. On guitar it is more awkward than the D or A equivalents, because C already spans three frets and the F has to be added at the first fret of the high E string while the hand is stretched.
The notes
C, F, G. No third, and the fourth leans firmly toward the E it replaced. Releasing the finger resolves the chord, and that release is the whole point of playing it.
The same three notes read from F give Fsus2 — the same ambiguity every suspension carries, decided by the bass rather than by the fingering.
The suspension is also the oldest device in Western harmony still in daily use. It predates the guitar by centuries, and its function has not changed since: delay the third, then supply it.
On the fretboard
The usual voicing keeps the C shape and adds the F on the high E string at the first fret. A four-string version drops the low C and is easier to reach at speed.
Because the stretch is uncomfortable, players often capo or use a different voicing entirely — the chord is common in songs but not in casual playing.
Where it shows up
In the key of C before the tonic, and in the key of G as a suspended IV. Worship and folk music use it constantly, almost always resolving within the bar.
It also appears as a way to keep a static C moving: alternating C and Csus4 provides motion with no harmonic change, and the figure is old enough to be invisible.