Depending on the number of intervals, chords can be defined in different ways, be it diads (two-note chords), triads (three-note-chords containing a root, third, and fifth) or, like we’ll learn in this lesson, four-part chords. These types of chords can be constructed in countless different ways, and make up the harmonic foundation for scales in music. A strong understanding of intervals will allow you to go from simply memorizing chord shapes to being able to build them yourself.