Bb 7b13 (Bb7b13)
Also written as A# 7b13 (A# and Bb are the same key).
Notes in Bb 7b13
Inversions
Same notes as Bb 7b13, 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 (Bb7b13/D)
2nd inversion
E# in the bass (Bb7b13/E#)
3rd inversion
G# in the bass (Bb7b13/G#)
4th inversion
F# in the bass (Bb7b13/F#)
Open voicings
A close-position chord like Bb 7b13 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
G# on the bottom
Drop 3
E# on the bottom
Bb 7b13 is built from A#, D, E#, G# and F#.
A dominant seventh with a flattened thirteenth, which is the same pitch as a sharpened fifth an octave up. It darkens a plain dominant just enough to pull harder toward its resolution, and it is one of the most common altered colors in jazz comping.