What's a Triad in Music?
A triad is a set of three notes, root (R), third (3) and fifth (5) stacked in third that can be played simultaneously (chord) or one by one (arpeggio).
There are four types of triads that are major (1-3-5), minor (1-b3-5), diminished (1-b3-b5) and augmented (1-3-#5).
What Are Upper Structure Triads?
Before tackling this musical concept, it is important to have a strong knowledge of the main important triads on guitar.
Any self-respecting guitarits must be able to hear, recognize and play any types of triads (minor, major, diminished, augmented) using different voicings (root, inverted) and positions (close and open).
Upper structure triads are three adjacent notes built from the structure (1-3-5-7) of any seventh chord/arpeggio containing one (or more) extra note beyond the octave.
These notes are the 9, 11 and 13 respectively 2, 4 and 6 up one octave.
Keep in mind that the 11 is an avoid note because it clashes with the third.
Let see what are the upper structure triads taken from the three most important chord types : minor, major and dominant.