A# Suspended 4th (A#sus4)
Also written as Bb Suspended 4th (Bb and A# are the same key).
1+4+5
Notes in A# Suspended 4th
A# (root)D#E#
Inversions
Same notes as A# 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
A# in the bass
1st inversion
D# in the bass
2nd inversion
E# in the bass
A# Suspended 4th is built from A#, D# and E#.
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.