The Major 6.
Used in a chord, this is one of my favorite sounds.
We identify the Major 6 by playing the first and sixth degrees of the Major scale. The formula for this chord in full would appear like this:
1 3 (5) 6 (7) - typically you might find yourself forced to drop either the 5 or 7 on guitar. It is possible to play all tones at once. Some cases however, require that at least one note is moved to a new octave. See the examples below: