Bb Suspended 2nd (Bbsus2)
Also written as A# Suspended 2nd (A# and Bb are the same key).
1+2+5
Notes in Bb Suspended 2nd
A# (root)B#E#
Inversions
Same notes as Bb Suspended 2nd, 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
B# in the bass (Bbsus2/B#)
2nd inversion
E# in the bass (Bbsus2/E#)
Press A#, B# and E# together on the keyboard and you're playing Bb Suspended 2nd.
Suspended chords pull the third out entirely, so they land somewhere between major and minor rather than picking a side. Sus2 fills the gap with a major second sitting close to the root, which gives it an open, slightly hollow color. It's a favorite way to add movement to a strummed or arpeggiated part without changing the underlying harmony.