Bb Augmented 7th
Introduction
Enharmonic equivalent: B♭ is enharmonically equivalent to A♯. See A# Augmented 7th.
Notes
Bb Augmented 7th Inversions
| Position | Notes |
|---|---|
| Root Position | Bb4 – D5 – Gb5 – Ab5 |
| 1st Inversion | D5 – Gb5 – Ab5 – Bb5 |
| 2nd Inversion | Gb5 – Ab5 – Bb5 – D6 |
| 3rd Inversion | Bb4 – D5 – Gb5 – Ab4 |
Key Signature
The key of Bb Augmented 7th has 2 flats: B♭, E♭.
Theory: Intervals
The Bb Augmented 7th is built by stacking intervals from the root note. The formula R-M3-A5-m7 describes the scale degrees used. The intervals P1-M3-A5-m7 show the distance between each note in the chord.
Bb Augmented 7th — Frequently Asked Questions
What notes are in the Bb Augmented 7th chord?
The Bb Augmented 7th chord (Bb+7) contains four notes: Bb (root), D (major third), F# (augmented fifth), and Ab (minor seventh). It combines an augmented triad with a minor seventh.
How does Bb Augmented 7th differ from Bb Dominant 7th?
Both contain Bb, D, and Ab. Bb+7 has F# (augmented fifth) while Bb7 has F (perfect fifth). The raised fifth adds extra tension and chromatic pull.
How is Bb Augmented 7th used in music?
Bb+7 is an altered dominant resolving to Eb Major. The F# pulls up to G while Ab pulls down to G — converging on the third of Eb. Eb is a common jazz and brass key, making Bb+7 a frequently used altered dominant.
What genres use Augmented 7th chords?
Augmented 7th chords are common in jazz, gospel, blues, and R&B. Bb+7 appears frequently in jazz because Eb Major is one of the most common jazz keys.
What songs use Augmented 7th chords?
Augmented 7th chords appear in jazz standards and gospel. Bb+7 resolves to Eb Major, appearing in many big band and jazz ensemble charts.
What is the difference between +7 and 7#5?
They are the same chord. Bb+7, Bb7#5, and Bbaug7 all refer to Bb Augmented 7th.
Practice Tips
- Play Bb7 then raise F to F# — hear the augmented fifth's extra chromatic tension.
- Practice Bb+7 → Eb Major. F# and Ab both resolve to G — converging voice leading.
- Compare Bb+7 with Bb7 — both target Eb, but +7 adds richer colour and drama.
- In jazz: Fm7 → Bb+7 → Ebmaj7 adds sophistication to the ii–V–I in Eb.
- Bb+7 is powerful in gospel piano — try it before the tonic for emotional intensity.
- The augmented triad (Bb–D–F#) divides the octave into three equal major thirds.