Harmony: Major Scale and Scale Degrees

Most music is still based on the harmony derived from the major scale. Each position or "Scale Degree", no matter what the key, has a harmony associated with it. One can construct a triad based on each degree, using only the notes of the scale, which has a particular mode and function for that degree

For example, in the C-Major Scale: C,D,E,F,G,A,B, each note is assigned a scale degree, in order, named by a Roman numeral. The triads are stacked thirds based on the scale. For example, I is the chord C-E-G which is a C-major triad. Each major triad is constructed on a root, the scale degree, a major third and a perfect fifth. Other Major triads are the ones constructed on IV: F-A-C, F-major and V: G-B-D, G-major all constructed within the C-Major Scale.

Triads constructed on The second, third, and sixth degree are minor triads that we designate with lowercase roman Numbers: ii, iii, vi. In the C-Major scale these would be D-Minor, E-Minor, and A-Minor Triads. The minor triad consists of the scale degree or root, a minor third and a perfect fifth.

The triad based on the Seventh Degree of a major scale is special. It is a diminished triad. In the C-Major Scale this is the B-diminished triad B-D-F, the interval B-F is a diminished fifth. It is also a tritone or Augmented Forth. This is inherently dissonant and in functional harmony is considered most unstable.

Triads described above are said to be in "root" position. If we make one of the other notes of the triad lower than the root the chord is said to be inverted. If we spell the C-major chord C-E-G, the root is lowest, this is root position. If we spell it G-C-E, it is inverted, because of the intervals created by putting the G lowest it is called I 6-4 inversion. If the E is lowest: E-G-C the interval between the top and bottom is a 6Th, this is called the I 6 inversion.