Three or more tones played simultaneously create a chord. Chords built in thirds are referred to as tertian. The name of a given chord identifies it’s structure and function in a harmonic progression. Some basic groups of chords follow.
Major chords are symbolized by M, ∆ or maj and consist of a major triad [1-3-5] , a major seventh and color tones [6-9-11-13].
Dominant chords are symbolized by the number 7,9,11,or 13 and consist of a major triad [1-3-5] , a minor seventh and color tones [9-11-13 etc.].
Minor chords are symbolized by -, m, or min and consist of a minor triad [1-b3-5] ,a minor seventh and color tones [ 6-9-11-13].
Diminished chords are symbolized by °7 or dim7 and consist of a diminished triad
[1-b3-b5] and a diminished , or double flat ,seventh.
Augmented chords are symbolized by + or aug and consist of an augmented triad
[1-3-#5] a minor seventh and color tones [9-11-13]