A chord is 3 or more notes that harmonise.   (I will use upper and lower case to show the same note in different octaves: C is an octave lower than c, for example.)   A simple chord is made of notes 1, 3 and 5 counting 1 as the root of the chord.   So the chord of C major is made up of the notes C E and G.   When a chord is major, the interval between the root and the 3rd note (C and E in the example) is 2 whole tones, and the interval between the 3rd and