AKA: A6, A6th, Aadd6, AM6, A Maj6, A Major sixth, A major6, A sixth
Major 6th chord
A major 6th chord is a four-note chord that contains the Root, the 3rd, the 5th, and the 6th of the major scale. In terms of intervals, a major sixth chord contains a major 3rd, perfect 5th, and major 6th. In other words, it’s a major triad with an added 6th.
The formula for major chords is R, 3°, 5°, 6°. For example, in C6 we have the notes C, E, G, A.
On a standard bass accordion, you can play major 6th chords by combining the Root with the minor chord of its 6th interval. For example, if C is the Root, adding an A minor you get a C6(5th omitted). You should add the major chord of the Root to get a full 6th chord but the 5th doesn’t add any tension so it can be omitted.
Major 6th chords are very common in pop, rock, and jazz music.
A, C#, E, F#
R, 3°, 5°, 6°
A + F#m (B♭♭ + G♭m)
4 + 2 or 5 + 2
2 + 5 or 2 + 4 on counter bass