Originally Posted by: darickmendes

So basically when transforming the chords from major to minor or dominant 7 or major 7 , the first and fifth notes don't change only third changes ?

Yes, the 3rd is the note that is either major or minor. And the 7th is an added note.

A major: a (1) - c# (M3) - e (5)

A minor: a (1) - c (m3) - e (5)

A7 : a (1) - c# (M3) - e (5) - g (m7)

A major 7: a (1) - c# (M3) - e (5) - g# (M7)

A minor 7: a (1) - c (m3) - e (5) - g (m7)