The names of the degrees · The major scale · Music theory
Each degree has its name. I is the tonic; II, the supertonic; III, the mediant; IV, the subdominant; V, the dominant, and VI, the submediant. VII is the…
The names of the degrees
Each degree has its name. I is the tonic; II, the supertonic; III, the mediant; IV, the subdominant; V, the dominant, and VI, the submediant. VII is the leading tone, because it lies a half step below the tonic and tends to rise to it.
The tonic, subdominant and dominant (I, IV and V) are the tonal degrees: they define the key, and its main chords are built on them. The mediant and submediant (III and VI) are the modal degrees: they change from major to minor and decide which mode it is.
The names make sense by position: the dominant is a 5th above the tonic and the subdominant, a 5th below; the mediant lies halfway from the tonic to the dominant, and the submediant, halfway from the tonic down to the subdominant.
Degrees that push and degrees that rest
Not all notes of the scale weigh the same. I, III and V, the notes of the tonic chord, are stable. The others tend to move toward them: VII rises to I, a half step away; IV falls to III, also a half step; II and VI lean on their neighbors.
This tendency explains why a melody sounds finished when it ends on the tonic, and why the leading tone, if it does not rise, leaves something pending. It is also the basis of the voice-leading rules of harmony.