> C9, C11 or C13 respectively instead of, say a Csus2, Csus4 That's actually not correct. sus, as in "suspended", implies that the third is absent from the ch

> C9, C11 or C13 respectively instead of, say a Csus2, Csus4 That's actually not correct. sus, as in "suspended", implies that the third is absent from the chord. Cadd2 or Cadd4 would be more correct. A major chord with an added forth is kind of a weird sound, however -- too unstable, the fourth wants to resolve. add2 chords are fairly common, though!