A Major Triad

Chord Tones: A Major Triad

Symbol: M, maj, (none) — Formula: 1-3-5

Chord Notation

Roman numeral (e.g. I, IV, V) and Nashville Number notation are key-dependent. See Keys pages for chord function within specific keys.

Inversions

Harmonic Function

The A major chord commonly functions as the submediant (vi) in C major or dominant (V) in D major. Its harmonic role varies by key — in major keys it provides stable harmonic grounding.

The major triad is the most fundamental chord in Western music, built from the root, major third, and perfect fifth. It has a bright, stable, and resolved sound. The A Major Triad specifically contains 3 notes: A, C♯, E (formula: 1-3-5). On guitar, A-rooted chords anchor to the open A string (5th string), and barre chord shapes rooted on A form the basis of the "A-shape" CAGED system. Blues, rock, and country music use A-rooted chords extensively — the classic 12-bar blues often starts on A, and many rock power chord riffs center on the open A string.

Common Progressions

The A Major Triad frequently appears in these progression patterns (shown in Roman numeral notation relative to key):

• I-IV-V-I
• I-V-vi-IV

Songs Featuring the Major Triad

Well-known songs where the A Major Triad — or this chord type — plays a prominent role:

• Let It Be – Beatles
• Don't Stop Believin' – Journey
• Imagine – John Lennon

Tuning Frequencies Across Temperaments

Frequencies shown at A=440 Hz. View full temperament data for any note.

Scales Containing the A Major Triad

These scales include the A Major Triad as a diatonic or characteristic chord: