Bb Major 9#11 (Bbmaj9#11)
Also written as A# Major 9#11 (A# and Bb are the same key).
Notes in Bb Major 9#11
Inversions
Same notes as Bb Major 9#11, 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 (Bbmaj9#11/D)
2nd inversion
E# in the bass (Bbmaj9#11/E#)
3rd inversion
A in the bass (Bbmaj9#11/A)
4th inversion
B# in the bass (Bbmaj9#11/B#)
5th inversion
E in the bass (Bbmaj9#11/E)
Open voicings
A close-position chord like Bb Major 9#11 can sound cluttered in the middle of the keyboard. Jazz players open it up by dropping one note down an octave, spreading the same notes wider without changing the chord.
Drop 2
A# on the bottom
Drop 3
A on the bottom
Press A#, D, E#, A, B# and E together on the keyboard and you're playing Bb Major 9#11.
The fuller Lydian chord: a major ninth plus the sharpened eleventh. It has the warm settled base of a major ninth with a bright shimmer on top. Jazz and fusion players often use it as a static tonic that never needs to resolve.