ACEG

ACEG denotes the four pitch classes A, C, E, and G. In Western music theory, this collection forms an A minor seventh chord (Amin7) when voiced as A–C–E–G. The intervallic structure is a minor third from A to C, a major third from C to E, and a minor seventh from A to G. The same four notes arranged in different orders provide inversions: C–E–G–A, E–G–A–C, and G–A–C–E. This sonority is common across genres, used for its mellow color and to connect harmonies; in the key of C major, ACEG corresponds to the vi7 chord, Amin7.

In notation, ACEG is the pitch-class set; the chord-symbol representation is Am7. The collection can also be extended or altered by adding tensions or modifying a tone, but the basic ACEG set remains a standard Amin7 sonority.

Outside music, ACEG is not tied to a single widely recognized meaning and may function as an acronym in various organizations or projects depending on context. See also Am7, piano voicings, music theory basics.