The Augmented Major Seventh Chord

Take a major seventh chord and stretch the fifth up a half step, and you get the one seventh-chord quality the major scale can’t produce — harmonize any major scale in sevenths and you’ll find majors, minors, dominants, and a half-diminished, but never this. That’s not a flaw; it’s the whole point. This chord is bright, unstable, and shimmering, and it exists because the melodic minor and harmonic minor scales both hand you a raised fifth as a byproduct of raising the seventh degree.

What’s In It and Why It Sounds Unfinished

Stack a major third, an augmented fifth, and a major seventh on the root:

Cmaj7♯5 = C–E–G♯–B (1–3–♯5–7)
E♭maj7♯5 = E♭–G–B–D
Fmaj7♯5 = F–A–C♯–E

Notice the embedded The Augmented Triad — C–E–G♯ — sitting under a major seventh. Where a plain Major Seventh Chord has a stable perfect fifth anchoring it, here the fifth has been pulled sharp, so the chord never quite settles; it just shimmers in place. That instability is exactly why it rarely gets treated as a chord that “resolves” the way a dominant does — it’s closer to a held breath than a cadence point.

Where It Actually Lives: Degree III of Minor

This chord isn’t an exotic invention laid on top of the major scale — it falls straight out of minor-key harmony. Raise the seventh degree of a minor scale (which is exactly what harmonic minor and the ascending melodic minor both do to create a leading tone), and the triad built on the third degree comes out augmented, with a major seventh sitting on top by default.

C melodic minor = C D E♭ F G A B → chord on ♭III (E♭) = E♭–G–B–D = E♭maj7♯5
C harmonic minor = C D E♭ F G A♭ B → chord on ♭III (E♭) = E♭–G–B–D = E♭maj7♯5 (identical spelling here — the difference between the two parent scales shows up on degree 6, not degree 3)

So whenever you see a ♭IIImaj7♯5 borrowed into a minor key — E♭maj7♯5 in C minor, for instance — you’re hearing a color pulled straight from Modal Interchange with the melodic- or harmonic-minor family, not an isolated novelty chord.

The Native Scale: Lydian Augmented

Every chord wants a scale that supplies its tones with no clashes, and for maj7♯5 that scale is the Lydian Augmented Scale — the third mode of melodic minor.

C Lydian Augmented = C D E F♯ G♯ A B (1–2–3–♯4–♯5–6–7)

Play that scale over Cmaj7♯5 and there are no avoid notes: the ♯4 and ♯5 aren’t tensions layered on top of the chord, they’re structural members of the scale the chord was built from. Compare that to trying to use plain Lydian (which has a natural 5th) — it simply doesn’t contain the chord tone you need. If you’d rather stay closer to harmonic minor’s flavor, the first mode of harmonic minor (Ionian ♯5: 1–2–3–4–♯5–6–7) works too, differing only in a natural 4th instead of a raised one — a subtler, less floaty alternative discussed further under Melodic Minor Applications.

Voicing It as a Slash Chord

Because the chord is really “major triad built on the 3rd, over the root,” it voices beautifully as an upper-structure triad or a plain slash chord:

E/C = E–G♯–B over a C bass = C–E–G♯–B = Cmaj7♯5

Pianists lean on this constantly: playing a simple major triad a major third above the root, without ever spelling the root’s own fifth, delivers the whole ♯5 color cleanly. It’s also worth keeping this chord straight from its cousin the Minor-Major Seventh Chord — mMaj7 pairs a minor third with a perfect fifth (C–E♭–G–B), a dark, “spy movie” sound, while maj7♯5 pairs a major third with a sharp fifth — bright where mMaj7 is shadowy, and unstable where mMaj7 is merely tense. Don’t confuse it either with The Augmented Dominant, which shares the raised fifth but carries a flat seventh and genuine dominant pull; maj7♯5 sits still.

♫ Listen

Miles Davis Quintet — “Iris” (Wayne Shorter, composer) (E.S.P., 1965): a slow-moving ballad built on sustained maj7♯5 sonorities — listen for how Herbie Hancock’s comping lets the ♯5 shimmer rather than resolve, suspending harmonic motion for whole phrases.
Gerry Mulligan Quartet with Chet Baker — “My Funny Valentine” (Pacific Jazz, 1952): the descending line cliché over C minor passes through Cm(maj7) — which is a rootless Cm(maj9), i.e. E♭maj7♯5 in all but the bass note — so listen for that raised-seventh shimmer in the very first bars under Baker’s melody.