B♭ Suspended 4th Chord (Bbsus4, A#sus4) on Piano
The Bbsus4 chord (Bb suspended 4th) is built from 3 notes: Bb – Eb – F. It is also written as A#sus4.
Play these notes on a MIDI keyboard, your computer keyboard, or the on-screen keys and ChordKeys will name the chord back to you.
Notes and intervals
| Note | Degree | Interval from Bb | Semitones |
|---|---|---|---|
| Bb | 1 | root | 0 |
| Eb | 4 | perfect 4th | 5 |
| F | 5 | perfect 5th | 7 |
Inversions
Rearranging which note sits at the bottom gives you 3 playable voicings of the same chord. Inversions let you move between chords with less hand movement.
| Voicing | Notes | Bass note |
|---|---|---|
| Root position | Bb – Eb – F | Bb in the bass |
| 1st inversion | Eb – F – Bb | Eb in the bass |
| 2nd inversion | F – Bb – Eb | F in the bass |
How the suspended 4th chord is built
Every suspended 4th chord uses the same interval formula: 1 (0 semitones), 4 (5 semitones), 5 (7 semitones). Starting on Bb and applying that formula produces Bb, Eb, F. Learn the formula once and you can build a suspended 4th chord on any of the twelve roots.
Keys that contain Bbsus4
Every note of Bbsus4 belongs to these keys, so it will sit naturally in a progression written in any of them.
Other chords on Bb
Suspended 4th chords on other roots
Frequently asked questions
What notes are in a Bbsus4 chord?
A Bbsus4 chord contains the notes Bb, Eb, F. Those are the 1, 4, 5 degrees measured from the root note Bb.
How do you play Bbsus4 on piano?
Place your thumb on Bb, then add Eb and F above it. With a right hand in root position the common fingering is 1–3–5.
Is Bbsus4 the same as A#sus4?
Yes. Bbsus4 and A#sus4 are enharmonic equivalents — they sound identical and use the same piano keys. Which spelling you use depends on the key you are playing in.