AKA: EM, E magg, EMaj, Emaj, E Major
A major chord is a triad built from the Root, 3rd, and 5th notes of the major scale. It’s built by combining a 3rd major interval with a 3rd minor interval, for example in C Major we have a major 3rd interval which is C-E and a minor 3rd interval, which is E-G.
Its sound is bright and happy.
The formula for major chords is R, 3°, 5°
On a standard bass accordion, major chords are right near the bass buttons column, on the 3rd column (or on the 2nd column if your accordion doesn’t have the counter-bass column).
E, G#, B
R, 3°, 5°
E + EM (F♭ + F♭M)
4 + 3