A# aug Piano Chord

Piano Diagram of A# aug in Root Position

An A# augmented chord is an augmented triad built upon the key of A-sharp. To get an A# augmented chord, you combine the root (A#), the major 3rd C_x (“C double sharp”, equivalent to a natural D), and the sharp 5th note E_x (which is equivalent to an F#) from the A-sharp scale. Keep reading to get a better grip on the music theory behind this chord.

 

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A# aug Chord Inversions

 

A# aug has a total of 2 inversions:

Piano Keyboard Diagrams

Inversions Equivalencies

One interesting feature of augmented chords is that each inversion of the chord produces a different augmented chord. For example, if you take the first inversion of an A# augmented chord, you get a D augmented chord (C_x is equivalent to D). And if you take the second inversion of an A# augmented chord, you get an F# (E_x) augmented chord.

So, you only really need four different augmented chords to cover all the possible keys, because all the other augmented chords can be found by inverting these four chords.

 

 

Notice how each of the four distinct augmented chords contains a unique combination of three notes, which can be rearranged into three different chord inversions. By utilizing these four chords and their inversions, it’s possible to cover all 12 keys.

Keep in mind that the selection of C, C#, D, and D# is arbitrary, as you could use any other series of unique augmented chords to build them all.

 

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Music Theory and Harmony of A# aug

 

Augmented chords are typically found on the third degree of both the melodic and harmonic minor scales, where they are intended to function as mediant chords.

F_x Melodic Minor Scale

F_x Harmonic Minor Scale

 

However, in practice, they are not commonly used in this way. Instead, augmented chords are often used as a leading tone to resolve to a major or minor tonic chord.

But before we explore the chords that can follow an A# augmented chord, let’s take a closer look at how to build it.

 

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Building the A# aug Chord: Different Approaches

 

Starting from the A# Major Scale

Keeping as reference the major scale, build the augmented chord, which consists of the Root, major 3rd, and sharp 5th. Keep in mind that A# major is a theoretical key since it has many sharp in its key signature, so it could be easier using its enharmonic equivalent chord Bb aug.

 

 

 

• Start from the root note A#.
• Add the major 3rd C_x (D).
• Raise the 5th note, E# (F) by one half-step to get E_x (which is equivalent to F#.)
• Combine the root note A#, the major 3rd C_x and the augmented 5th E_x to form the A# augmented chord.

You can apply the formula R, 3, #5 to build any augmented chord.

 

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by Combining 3rds

An augmented triad is a chord consisting of two stacked major 3rds.

3 + 3 = aug Chords

To build an augmented triad on A#, you would start from the root note A#. Next, you would add a major third interval above A# to obtain the note D. In this context, we would call this note C_x (C double sharp) to preserve the chord’s basic structure. Finally, you would add another major third interval above D (C_x) to get the note F#. Once again, we would refer to this note as E_x for consistency.

The resulting A# augmented triad would consist of the notes A#, C_x, and E_x.

 

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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#, Cx, Ex) 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, Cx Major, or Ex (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, Cx minor, or Ex (F#) minor. This is useful in minor keys that borrow a V7 from the harmonic minor: A# aug can stand in for A#7, and, through its inversions, for Cx7 and F#7 as well. In practice the strongest fit is the augmented chord that shares its root with the dominant it replaces (A# aug for A#7); using it in place of Cx7 or F#7 really means using an inversion of Cx 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 Ax (B) minor, D# minor, or 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 Ax (B) Major, D# Major, or 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 (Ex) rises a half step to Fx, 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 Cx aug and Ex/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 Ax and Gx Major are theoretical keys, we refer to their enharmonic equivalents, B and A Major.

• Resolving A# aug to D# major, the chord functions as V+ in D#. This is its most idiomatic use, a substitute for A#7 whose raised fifth (Ex) 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 Fx major, A# aug substitutes for the V+ (Cx aug) because it is an inversion of Cx aug, which replaces Cx7.
• Ex (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 E7, since A# and E are a tritone apart.

 

*Since Ax minor has 7 sharps, we refer to its enharmonic equivalent, B 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 Cx aug and Ex aug, and each augmented chord can stand in for the dominant 7th on its own root, A# aug can replace A#7, Cx7, or Ex7 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 (E#ø → A#7#5 → D#m)

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#, Cx, Ex, Gx); 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 G#7, for instance, augmented triads built on the root (G#) and on the 9th (A#) spell out a G#9#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 Ex (the augmented fifth of A# aug), then to Fx (turning the chord into A#6), then on to G# (making A#7, a secondary dominant that leans toward the IV chord, D#). That single rising line, E# – Ex – Fx – 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# – D#m, 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# → Ex → Fx → G# while A# and Cx 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 A#7 acts as V7/IV, so the whole line E# → Ex → Fx → 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 Ex is the climbing inner voice on the way from the tonic to A#6, 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# → Ex → Fx) drives the motion toward the borrowed minor iv.

 

ii – V⁺ – I with the augmented lift resolved (B#m7 → 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 Ex resolving up to Fx.

This is the ii–V–I from the table above, with the augmented fifth (Ex) rising a half step into Fx, 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 Fx, or of Ax/B, 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 A#6, 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 Ex rises a half step to Fx, 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 Ex then to Fx, 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 Fx → F# (Ex) → 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: Ex strains toward Fx but never arrives, holding the listener in suspense.

 

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Alternative Names for A# aug

• A#+
• A#+5
• A#aug
• A#(#5)
• A#(5#)
• A#(5+)
• A#(#5+)
• A#aug5
• 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.”