A triad chord consists of 3 different notes. When the root of the chord is at the bottom, all chord tones are stacked from the chord root upwards either on successive lines, or in successive spaces.
There are four qualities of triad chords :
major - minor - diminished - augmented
The major triad is formed by the tonic (1st), 3rd and 5th note of the major scale which starts on the chord root. For example the C major triad is formed by the notes C, E and G.
C 1
D 2
E 3
F 4
G 5
A 6
B 7
The other triad qualities are derived from the major triad chord.
To form from a major triad (1 - 3 - 5) :
a minor triad -> lower the 3rd : 1 3 5 ---> 1 b3 5 (in C : C E G ---> C Eb G = Cm)
a diminished triad -> lower the 3rd and 5th : 1 3 5 ---> 1 b3 b5 (in C : C E G ---> C Eb Gb = Co)
an augmented triad -> raise the 5th : 1 3 5 ---> 1 3 #5 (in C : C E G ---> C E G# = C+)
