Bb7 takes the stable major triad and gives it somewhere to go. The new voice is ; together the notes are Bb, D, F and Ab.
sits a whole step below the next root. In the pair below, that single arrival changes a major chord from a resting point into a dominant.
One repeated root moves down a whole step to the flat seventh. The other notes stay the same.
Follow that pull to , the major chord a fourth higher. The third rises while the flat seventh falls, closing around the new root.
Also written Bbdom7 or Bb dominant 7.
Bb7 in 3rd inversion puts Ab in the bass instead of Bb, the 7th 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.
4 of Bb7’s 22 shapes do this:4533xxxx6764x-11-12-10-11-xx-11-x-10-11-10
Bb7 is the V of E♭ major. Its third and seventh are a tritone apart, the most unstable interval there is, and each resolves by a half step into the I. The dominant a tritone away shares those two notes, so it resolves the same way.
Listen for: The dominant’s seventh falls a half step to the third of the I. Under the tritone substitute it is the same note.
In a blues, Bb7 is the home chord rather than a V: it moves to Eb7 and back without resolving. Its third and seventh each slide down a half step to become the seventh and third of Eb7, so the shape stays the same, one fret lower.
Listen for: Both notes above the bass drop one fret into the IV and come back: the third becomes the IV’s seventh.
In the turnaround in D♭ major, jazz players usually replace the vi chord with Bb7, and usually alter it.
Replace the VI7, II7 and V7 of a turnaround with their tritone substitutes and you get Amaj7, C7, F7, Bb7. Bb7 is the last, a half step above the I.
In which keys. Every note of Bb7 belongs to C minor and Eb major.
Contains Bb7 and adds ninth, eleventh and thirteenth.
Adds ninth, sharp eleventh and thirteenth, for a dominant sharp-eleventh color.
Contains Bb7 and adds flat ninth, sharp ninth, sharp eleventh 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.