A aug Piano Chord

Piano Diagram of A aug in Root Position

The A augmented chord is a three-note chord made up of A, C#, and E#: an A major triad with its fifth raised a half step. Built by stacking two major 3rds (A to C#, then C# to E#), it splits the octave into three equal parts, and that symmetry is the source of everything distinctive about the chord. The raised fifth (E#) is a restless note that wants to move up by a half step, which is why the augmented triad works best as a chord in motion rather than a point of rest: most often it acts as an altered dominant that leans into a tonic, or as a chromatic passing chord that fills in an ascending inner line. In this article we’ll look at how the chord is built, why its symmetry makes it interchangeable across three keys at once, and how it works in real progressions.

 

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A aug Chord Inversions

 

A aug has a total of 2 inversions:

Piano Keyboard Diagrams

Inversions and the Symmetry of Augmented Chords

Because the augmented triad is built from two equal major 3rds, its inversions are not just re-voicings of the same chord the way they are for major or minor triads. Each inversion of an augmented chord is itself an augmented chord with a new root.

Take the first inversion of A aug (C#, E#, A). Re-spelled from its lowest note, this is a C# augmented triad (C#, E#, G_x). The second inversion (E#, A, C#) is an E# augmented triad (E#, G_x, B_x), which sounds the same as an F augmented chord. In other words, A aug, C# aug, and E#/F aug are the same three pitches wearing three different names. The chord divides the octave into a perfect triangle, and you can enter that triangle from any of its three corners.

A practical consequence follows: there are only four distinct augmented chords in all of tonal music. Every augmented chord is an inversion of one of these four, and each of the four covers three keys at once.

 

Each of the four distinct augmented chords holds a unique set of three notes, and each can be voiced as three inversions, so together the four chords and their inversions account for all 12 keys. A aug lives in the second row: it is the same chord as C# aug and E#/F aug. The choice of C, C#, D, and D# as the four “parents” is arbitrary; any four roots a half step apart would generate the full set just as well.

 

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Music Theory and Harmony of A aug

 

The augmented triad does not belong to the major scale. The one place it occurs diatonically is on the third degree (III+) of the harmonic and melodic minor scales, where the raised leading tone supplies the augmented fifth. In F# minor, for example, the third-degree triad is A augmented. In practice, though, composers rarely treat III+ as a stable mediant. What makes the chord useful is the opposite of stability: the augmented fifth is a tendency tone that pulls upward, so the chord is almost always heard on its way somewhere, most often to a major or minor tonic as an altered dominant, or as a passing chord inside an ascending line.

F# Melodic Minor Scale

F# Harmonic Minor Scale

The augmented triad is also the core of two important scales. Raising the fifth of a dominant chord gives a 7#5, whose natural scale is the whole-tone scale (six notes a whole step apart, entirely symmetrical). Raising the fifth of a major-7th chord gives a maj7#5, whose scale is the Lydian augmented (the third mode of melodic minor). And stacking the three major triads a major 3rd apart produces the augmented scale, the six-note collection at the heart of Coltrane’s three-tonic system in “Giant Steps.” All three grow directly out of the augmented triad’s equal division of the octave.

But before we look at where A aug can go, let’s see how it is built.

 

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Building the A aug Chord: Different Approaches

 

Starting from the A Major Scale

Using the major scale as a reference, an augmented triad is the Root, the major 3rd, and the raised (sharp) 5th.

 

 

 

• Start from the root note A.
• Add the major 3rd, C#.
• Raise the 5th (E) by a half step to get E#.
• Combine A, C#, and E# to form the A augmented chord.

The same formula, R, 3, #5, builds an augmented triad on any root.

 

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by Combining 3rds

An augmented triad is simply two stacked major 3rds.

3 + 3 = aug Chord

Start on the root A, add a major 3rd to reach C#, then add another major 3rd to reach E#. The result, A, C#, E#, is the A augmented triad. Because both intervals are identical, the shape repeats no matter which note you treat as the bottom, which is exactly why the inversions produce new augmented chords.

 

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How to Use A aug in a Chord Progression

 

The augmented triad earns its place in three ways: as a substitute for a dominant 7th chord, as a chromatic passing chord that connects two diatonic harmonies, and as a pivot that exploits its symmetry to slip between distant keys. All three uses rest on the same fact: because the chord is built from equal major 3rds, moving any single voice by a half step turns it into a familiar major or minor chord. That is what makes it such an efficient hinge between harmonies, so it’s worth seeing exactly which chords sit a half step away.

 

Resolving A aug by Half-Step Voice Leading

Each of the three notes of A aug (A, C#, E#) sits a half step away from a chord tone of some nearby major or minor triad. By lowering or raising one or two of its notes, the augmented chord resolves smoothly into six major and six minor triads. The tables below lay out those moves; they are best understood as voice-leading shortcuts, not as a catalogue to memorize.

 

Lowering One Note: A aug to Major Chords

Lowering any single note of A aug by a half step yields a major triad:

 

Lowering one note turns A aug into A Major, C# Major, or E# (F) Major, one rooted on each note of the chord.

 

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Lowering Two Notes: A aug to minor Chords

Lowering two notes gives the three minor triads rooted on the same notes:

 

 

Lowering two notes gives A minor, C# minor, or E# (F) minor. This is useful in minor keys that borrow a V7 from the harmonic minor: A aug can stand in for A7, and, through its inversions, for C#7 and F7 as well. In practice the strongest fit is the augmented chord that shares its root with the dominant it replaces (A aug for A7); using it in place of C#7 or F7 really means using an inversion of C# aug or F aug.

 

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Raising One Note: A aug to minor Chords

Raising a single note gives three more minor triads:

 

 

Raising one note gives A# (Bb) minor, C_x (D) minor, or E_x (F#) minor.

 

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Raising Two Notes: A aug to Major Chords

Finally, raising two notes returns three major triads:

 

 

Raising two notes gives A# (Bb) Major, C_x (D) Major, or E_x (F#) Major. Taken together, the four tables show the augmented triad’s real advantage: from one symmetrical shape, a single half-step move reaches a dozen different triads.

 

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A aug as an Altered Dominant (V+)

 

The single most common use of the augmented triad is as an altered dominant. When A aug functions as V+ in the key of D, the augmented fifth (E#) rises a half step to F#, the third of the tonic, while the root moves down a fifth in the usual way. The result is a dominant with an extra voice pulling toward the tonic, which sharpens the sense of resolution. Because A aug shares its notes with C# aug and E#/F aug, the same shape can act as the altered dominant in three keys at once, though the clearest reading is always the one where the augmented chord shares its root with the dominant it replaces.

The tables below place A aug inside a ii–V–I, substituting it for the V chord. Try each progression both ways: plain dominant, then augmented, to hear what the raised fifth adds.

 

*Since A# and G# Major are theoretical keys, we refer to their enharmonic equivalents, Bb and Ab Major.

• Resolving A aug to D major, the chord functions as V+ in D. This is its most idiomatic use, a substitute for A7 whose raised fifth (E#) leans up into the third of D. This is the same augmented lift heard in the verse of “Take the A Train” and in the opening bars of the Beatles’ “Michelle.”
• In F# major, A aug substitutes for the V+ (C# aug) because it is an inversion of C# aug, which replaces C#7.
• E# (F) aug is likewise an inversion of the same chord and can substitute as well, though it is usually clearer to use the augmented chord that shares its root with the dominant.
• Tritone substitution: replacing a dominant with a chord a tritone away keeps the dominant function while changing its color. A aug can act as a tritone substitute for Eb7, since A and Eb are a tritone apart.

 

*Since A# minor has 7 sharps, we refer to its enharmonic equivalent, Bb minor.

In minor keys the dominant is usually borrowed from the harmonic minor so that it carries a raised third; the augmented triad slots naturally into that role. Since A aug shares its notes with C# aug and E# aug, and each augmented chord can stand in for the dominant 7th on its own root, A aug can replace A7, C#7, or E#7 in their respective keys, best of all when it keeps the same root as the dominant it stands for.

 

Minor ii – V⁺ – i with a 7#5 dominant (Eø → A7#5 → Dm)

Adding a b7 to the augmented triad gives a 7#5, the crunchiest altered dominant. This is the strongest way to hear A aug pulling into D minor, and it takes the whole-tone scale over the V chord.

 

The augmented major-7th sound (A^Δ#5)

Adding a major 7th instead gives a maj7#5, a lush, floating colour favoured by writers like Wayne Shorter (heard throughout “Iris”). It works as a tonic or as a III+ borrowed from the melodic minor.

A Maj7#5 is the A augmented triad with a major 7th on top (A, C#, E#, G#); here it colours the tonic before the phrase settles diatonically.

 

The augmented triad as an upper structure over a dominant

Jazz players also use the augmented triad as an upper structure: a bright triad shape in the right hand stacked over a dominant shell in the left. Over a G7, for instance, augmented triads built on the root (G) and on the 9th (A) spell out a G9#5, one of the most useful altered-dominant colours. The trick works because the augmented triad’s notes are all drawn from the whole-tone scale, the natural scale of a 7#5. One caution: because the augmented sound needs a natural 9th, it pairs with 9#5 but clashes with a b9 or #9, so it is not a substitute for every altered dominant.

 

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A aug as a Chromatic Passing Chord (the Augmented Line Cliché)

 

The second great use of the augmented triad is as a passing chord that harmonizes an ascending inner voice over a static bass. Hold an A major chord and let one inner voice climb by half steps: E (the fifth) rises to E# (the augmented fifth of A aug), then to F# (turning the chord into A6), then on to G (making A7, a secondary dominant that leans toward the IV chord, D). That single rising line, E – E# – F# – G, is the augmented line cliché, and it is one of the most recognizable gestures in popular song.

Lesley Gore’s “It’s My Party” is a textbook case: its chorus runs A – A+ – D – Dm, the augmented chord lifting the tonic straight into the subdominant. You also hear the device under sustained tonics in “Take the A Train,” in the Beatles’ “Oh! Darling” (which opens on an augmented V), and throughout the James Bond themes, where the raised fifth supplies that signature suspenseful lift. The progressions below show A aug doing this work; each keeps A in the bass while the harmony brightens step by step.

 

Ascending line cliché (I → I⁺ → I⁶ → I⁷)

The complete rising line over a held A, ending on a secondary dominant that pushes to the IV chord.

The inner voice climbs E → E# → F# → G while A and C# stay put.

 

Extended line cliché into the subdominant (I → I⁺ → I⁶ → I⁷ → IV)

The full “Take the A Train” gesture: the rising line resolves onto IV, with the maj7 giving the arrival some weight.

The A7 acts as V7/IV, so the whole line E → E# → F# → G lands naturally on D.

 

Line cliché into the minor subdominant (I → I⁺ → I⁶ → iv)

The same rising line resolving into a minor iv. A aug works as the passing chord: its E# is the climbing inner voice on the way from the tonic to A6, before the phrase settles on D minor. This is the classic “My Funny Valentine” / James Bond inner-voice motion, and it is exactly the A+ that hangs over the intro of the Beatles’ “I Want You (She’s So Heavy)” before dropping to D minor.

The rising fifth (E → E# → F#) drives the motion toward the borrowed minor iv.

 

ii – V⁺ – I with the augmented lift resolved (Bm7 → A aug → D^Δ)

Instead of a bare three-chord turn, this places A aug as a true V+ of D inside a full ii–V–I, its E# resolving up to F#.

This is the ii–V–I from the table above, with the augmented fifth (E#) rising a half step into F#, the third of D.

 

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A aug as a Pivot: Modulating through Symmetry

Because A aug belongs equally to three keys, it makes an ideal pivot for modulation. The same three notes can be heard as V+ of D, of F#, or of A#/Bb, so a single augmented chord can turn a corner into any of those areas without preparation. The simplest device is to sit on a static tonic and colour it with the augmented chord before moving on; it “adds interest to a series of static measures on a single chord,” as the older analyses put it. The turnaround below uses A aug as a neighbour on both sides of a bright A6, a compact way to animate a bar that would otherwise hold a single chord.

I I⁺ I⁶ I⁺ I

 

A aug in Famous Songs

 

Augmented triads are rare in popular music, which is exactly why they stand out when they appear. Songwriters reach for them at moments that need a lift, a hint of unease, or a strong pull toward the next chord. The examples below are shown in the same key as the rest of this article; in the original recordings they appear in whatever key the song happens to sit in, but the harmonic function is identical once transposed. Play each one, then swap the augmented chord for a plain major or dominant to hear exactly what the raised fifth contributes.

 

The doo-wop opener (the “Oh! Darling” gesture)

One of the most famous uses of an augmented triad in rock opens the Beatles’ “Oh! Darling”, where a V+ chord launches the vocal before the song settles into a doo-wop progression. Transposed so that A aug is the dominant, the chord resolves up to the tonic a fourth above.

The augmented fifth E# rises a half step to F#, the third of the D major tonic, driving the resolution.

 

The rising line cliché (the “(Just Like) Starting Over” gesture)

John Lennon’s “(Just Like) Starting Over” uses an augmented chord that arises from ascending chromatic motion over a held root, the tonic climbing to its sharpened fifth before moving on. This is the same ascending line cliché shown earlier, framed here as a real-song example.

E rises to E# then to F#, the tonic staying under the moving inner voice.

 

The descending line cliché (the “All My Loving” gesture)

The Beatles’ “All My Loving” features augmented colour in its harmony arising from a descending chromatic line. Reframed on a held A, the fifth falls by half steps, the mirror image of the rising cliché above.

The fifth descends F# → F (E#) → E, creating the classic falling inner voice.

 

The hanging dominant (the “I Want You (She’s So Heavy)” gesture)

On Abbey Road, “I Want You (She’s So Heavy)” ends a section on a dramatic, unresolved augmented V chord that leaves the ear expecting a return to the minor tonic. Placed on the tonic’s dominant as V+, it hangs over the relative minor without resolving, all tension and no release.

The chord is left hanging: E# strains toward F# but never arrives, holding the listener in suspense.

 

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Alternative Names for A aug

• A+
• A+5
• Aaug
• A(#5)
• A(5#)
• A(5+)
• A(#5+)
• Aaug5
• A(5aug)
• A(+#5)

 

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Conclusion

The augmented triad is a small chord with an outsized role. Its equal division of the octave means one shape covers three keys, its raised fifth makes it a natural altered dominant (V+), and its half-step voice leading lets it pass smoothly between diatonic chords or pivot into distant ones. The progressions here cover its core idiomatic uses: as a substitute dominant in ii–V–I, as the ascending line cliché over a static tonic (heard in “It’s My Party,” “Oh! Darling,” and countless film scores), and as a symmetric pivot. As an upper structure it also supplies the 9#5 altered-dominant colour prized in jazz. From these foundations the chord opens onto wider territory, including the whole-tone and augmented scales, the augmented major-7th sound favoured by writers like Wayne Shorter, and the three-tonic system behind “Giant Steps.”