A triad is constructed of the first, third and fifth notes of the major scale E major 1. Understand the Theory A key signature is the sharp signs next to the clef. In this case we have F sharp, C sharp, G sharp and D sharp. If you need help here please see the key signatures blog. The tonic triad is the 1st , 3rd and 5th note of the scale. When there is no key signature this triad requires an sharp sign in front of the G to make it a G sharp. It does not need a F sharp, C sh