A practical way to hear Bb11 is as held over the original root. The upper shape supplies the flat seventh, ninth, and : Bb, F, Ab, C and Eb.
Because that upper shape omits the dominant’s major third, the chord remains suspended. This bass-plus-shape sound is used mainly as V.
Also written Bb9sus4 or Bb dominant 11.
Bb11 in 2nd inversion puts F in the bass instead of Bb, the 5th of the chord. The notes are the same; what changes is what the bass line does, which is most of why you would reach for it — it lets the lowest voice move by step where the root would have jumped.
2 of Bb11’s 14 shapes do this:x8889813-x-13-13-11-x
Bb11 has the notes of the ii over the V’s root, so it can take the ii’s bar: Bb11, then Bb9, then Eb. The eleventh gives way to the third, and the V resolves as usual.
Listen for: The eleventh falls a half step to the third, then rises a half step into the root of the I.
In which keys. Every note of Bb11 belongs to C minor, C# major, Eb major, F minor, Ab major and Bb minor.
Contains Bb11 and adds major third and thirteenth.
Contains Bb11 and adds minor third and flat thirteenth.
Contains Bb11 and adds minor third and thirteenth.
The common shapes and the derived voicings come from different places, and both are explained in how this site is built.
Shows each chord the way this style would voice it, and marks which of its alternatives belong to the idiom.