Chord formulas for major and minor triads
Now we know how to construct major and minor scales, we can take the notes within them and start stacking them up together to play chords. While it’s possible to form simple two-note chords, the most basic form of chord in common usage contains three notes, and is known as a triad. Like scales, triads come in major and minor flavours, depending on the scales their notes (also known as chord tones) are taken from.
Take the C major scale as an example. It contains the notes C-D-E-F-G-A-B-C, as we’ve seen. If we use numbers to label the notes (or degrees) in the scale from 1 to 8, we can use these numbers to create formulas to build chords from. For instance, in a C major scale, C=1, D=2, E=3 and so on, until B=7. So, to build a C major triad, we need the notes numbered 1, 3 and 5 from the major scale; in other words, C, E, and G = C major. The same idea works when building minor triads from minor scales, too. Take the scale of A natural minor (which uses all the white notes too, from A to A): A-B-C-D-E-F-G-A. Taking the notes numbered 1, 3 and 5 from this scale – A, C and E – gives us an A minor triad.
Looking at it from the point of view of the intervals between the chord tones, the formulas are root + 4 semitones + 3 semitones for a major triad, and root + 3 semitones + 4 semitones for a minor triad. Using a combination of major and minor triads, it’s possible to play thousands of popular songs, so they’re pretty useful things to know!