Bb7

Bb7, or B-flat dominant seventh, is a dominant seventh chord built on B-flat. It consists of a major triad (B-flat major: B♭–D–F) with a minor seventh added (A♭), giving the pitch collection B♭–D–F–A♭.

In functional harmony, Bb7 functions as the dominant chord in keys where B-flat serves as the dominant scale degree. The most common context is as the V7 of E-flat major or E-flat minor, for example in the ii–V–I progression Fm7–Bb7–E♭ major (or E♭ minor). Because of its strong sense of resolution, Bb7 is frequently used to lead to an E-flat chord, and it appears in many jazz, pop, and classical progressions.

Voicings and inversions commonly used include root position (B♭–D–F–A♭), first inversion (D–F–A♭–B♭), second inversion (F–A♭–B♭–D), and third inversion (A♭–B♭–D–F). In practice, players often omit one of the chord tones for a more compact texture, especially in jazz voicings.

Alterations and extensions are common in modern practice, with Bb7 frequently expanded to include tensions such as Bb7(9), Bb7(13), or altered variants in specific genres. However, the basic Bb7 remains the dominant seventh chord built on B-flat.

See also: dominant seventh chord; V7 in major keys; ii–V–I progression.