A 6 Chord
How the A 6 chord is built: its notes, its interval structure, and where it fits.
The A 6 chord contains 4 notes: A – C# – E – F#. It belongs to the sixth family of chord qualities. Like every chord, it is defined by the distances (intervals) between its notes, not by any one instrument — which is why the same formula names the chord whether it is voiced on a fretboard, a keyboard, or a choir.