A7 Chord on Piano
A7 = A – C# – E – G (Root, Major 3rd, Perfect 5th, Minor 7th)
Fiddle and banjo players treat A as one of their most comfortable open keys, and A7 — spelled A, C#, E, and G — is the chord old-time and bluegrass piano accompanists reach for constantly to sit alongside them. The added G lands on a white key, so the four-note shape still needs only the single black key, C#, that the plain A major triad already required. Formally, A7 is the V7 of D major, resolving there with real classical force whenever the surrounding harmony calls for it.
The pinky simply extends one white key further than the A major triad already reaches, down to G, while the thumb and middle finger stay anchored on A and C# — a comfortable, approachable stretch for a four-note chord. The tritone between C# and G is what creates the restlessness, the same relationship behind every dominant seventh regardless of root. In old-time and bluegrass contexts, A7 often functions less like a strict classical dominant and more like a static color chord, looped for measures at a time the way fiddle tunes in A frequently treat it, only occasionally resolving formally into D major. Square dance callers and old-time fiddle bands treat A7 almost as a rhythmic device as much as a harmonic one, driving the beat forward through repeated pattern rather than aiming at any particular resolution.
Voicings
Root Position
1st Inversion
How to Practice It
Add the pinky's reach to G on top of an A major triad you already know well — a small, natural extension rather than a new shape to learn from scratch. Because this chord shows up so often in fiddle- and banjo-adjacent playing, practice it as a static vamp, holding it for several bars without moving, just as often as you practice its formal resolution into D major. When you do resolve it, slow down enough to actually feel the tritone between C# and G release into the D major triad rather than rushing past that moment of arrival.
Common Progressions
- A7 – D (V7 – I in D major), the classical dominant resolution
- A7 – D – G – D (V7 – I – IV – I in D major), stretching that resolution into a short phrase
- D – A7 – D (I – V7 – I), A7 working as a turnaround back to D
- A7 – A7 – A7 – A7, the static I7 groove a fiddle band would vamp on for measures at a time
- Bm – E – A7 (ii – V/V – V7 in D major), stacked dominants tightening the pull toward D
FAQ
- Why is A7 a staple of bluegrass and old-time piano accompaniment?
- A is a favorite open key for fiddle and banjo, so tunes written for those instruments settle there constantly, and A7 becomes the workhorse chord pianists reach for alongside them.
- Does A7 need more black keys than plain A major?
- No — the added note, G, is a white key, so both chords use only the single black key, C#, keeping A7 comparatively easy to reach.
- What interval gives A7 its restless quality?
- The tritone between C# and G, the chord's third and flattened seventh — the same unstable interval found in every dominant seventh, here pulling toward D major.
- Is A7 used more rhythmically than harmonically in old-time music?
- Often, yes — square dance and fiddle bands treat it as a driving rhythmic device as much as a chord aiming at resolution, keeping the beat moving forward through repetition rather than formal cadence.
- Is A7 hard to add on top of a triad a student already knows?
- Not at all — since the added note lands on a white key, it's simply one more pinky reach beyond the familiar A major shape, making A7 one of the easier four-note dominants to pick up.
- How does A7 compare physically to E7?
- Nearly identical — both need only the same single black key their plain triads already require, differing only in root, which is why the two shapes transfer easily once one is comfortable.
- Does A7 ever function as a secondary dominant?
- Yes — it can borrow briefly into a passage centered on another key, pointing toward D for a beat or two before the surrounding harmony carries on elsewhere.
A7 on other instruments: A7 on Guitar, A7 on Ukulele. Related: how chords are built, chord finder.