Dominant 7th b13
7b13
0 - 4 - 7 - 10 - 20Dom7 with minor 13th
About Dominant 7th b13
A dominant seventh flat thirteen chord is a dominant with a lowered thirteenth — in C that is C, E, G, B♭ and A♭, written C7♭13. The lowered thirteenth is the same pitch as a raised fifth, and which name a chart uses tells you whether the perfect fifth is expected to be present alongside it.
Notes and formula
The formula is 1 – 3 – 5 – ♭7 – ♭13, or 0 – 4 – 7 – 10 – 20 in semitones. The thirteenth is lowered a semitone from the natural one.
A♭ and G are a semitone apart, so a voicing that sounds both needs them far apart or the chord curdles. Most players drop the fifth, at which point the chord becomes indistinguishable in sound from a raised-fifth dominant.
Flat thirteen or sharp five
The two symbols describe the same pitch and different intentions. C7♯5 says the fifth has been raised and there is no natural fifth; C7♭13 says the fifth may still be there and this is a note above it.
In a big-band score the distinction matters, because it tells the section what to play. In a small group it usually does not, because nobody plays the fifth anyway.
How to play it
On guitar the practical form is x–3–2–3–1–x, sounding C–E–B♭–A♭ with the fifth omitted. Trying to include G makes the chord muddy and the shape unplayable.
On piano the useful voicing is C in the left hand, E–A♭–B♭ in the right. If the arrangement requires the natural fifth, it belongs at least a tenth below the flattened thirteenth.
Where it belongs
In minor-key cadences, where the lowered thirteenth is simply the sixth degree of the key still sounding. G7♭13 resolving to C minor uses E♭, which is diatonic to the destination.
That is the clearest way to hear the chord: it is a dominant that has already borrowed a note from where it is going.
Against the altered dominants
C7♭13 alters one degree and keeps everything else. C7alt alters the fifth and the ninth together and is a different animal — more chromatic, less tied to a key.
This chord is the mildest way to darken a dominant, which is why it appears in music that is otherwise entirely diatonic.
Scales that contain it
The fifth mode of harmonic minor fits exactly and is the classical answer: it has the major third, the flattened seventh and the lowered sixth the chord needs.
The altered scale fits too and adds altered ninths on top. The whole-tone scale does not, because it has no natural fifth and no perfect fourth — it turns the chord into something else.
Frequently asked questions
What notes are in a C7♭13 chord?
C, E, G, B♭ and A♭, with the fifth usually dropped in practice. On guitar, x–3–2–3–1–x.
Is ♭13 the same as ♯5?
The same pitch, a different instruction. Sharp five means the fifth has moved; flat thirteen means a note has been added above a fifth that may still be there.
Where does the chord come from?
Most often from a minor key: the lowered thirteenth is the sixth degree of the key the dominant is resolving to, so the chord borrows the destination's colour in advance.