C# Suspended 4th (C#sus4)
Also written as Db Suspended 4th (Db and C# are the same key).
1+4+5
Notes in C# Suspended 4th
C# (root)F#G#
Inversions
Same notes as C# Suspended 4th, with a different chord tone as the lowest note. Useful for smoother movement between chords instead of jumping around the keyboard.
Root position
C# in the bass
1st inversion
F# in the bass
2nd inversion
G# in the bass
Press C#, F# and G# together on the keyboard and you're playing C# Suspended 4th.
The other suspension raises the missing third up to a perfect fourth, which sits a half step above where the third would normally be. That closeness creates real tension, and it's why a sus4 chord so often falls straight back down into the plain major or minor triad on the same root a beat later.