Scale degrees

The seventh note of a major scale sits a half step below the tonic, which is why it is called the leading tone: the ear expects it to rise.

Numbers, syllables and names

Musicians have three ways to talk about the notes of a scale, and all three work in any key. The first is a number: the tonic is 1, the next note 2, and so on up to 7. Textbooks put a small caret over the number (1̂, 2̂, 3̂) to show that it means a scale degree rather than a count of beats. The second is a singing syllable from solfège: do, re, mi, fa, sol, la, ti. The third is a name that describes the job each note does in the key.

Numbers and syllables move with the key. In C major, 1 and do are C; in G major, 1 and do are G. This system is called movable do, and many choirs and ear-training classes use it because a tune sounds like the same pattern of syllables in every key. In the other system, fixed do, common in countries that speak Romance languages such as Italian and French, do always means C, whatever the key. This course uses movable do whenever it talks about scale degrees.

Names that describe a job

The scale-degree names come from where each note sits relative to the tonic. The tonic (1) is home, the note a piece usually ends on. The dominant (5), a fifth above, is the second most important note; the word comes from medieval music theory. The mediant (3) means middle, because it sits halfway between tonic and dominant. The supertonic (2) is the note just above the tonic, since super means above.

The sub- names mirror these below the tonic. The subdominant (4) is a fifth below the tonic, just as the dominant is a fifth above. The submediant (6) is a third below the tonic, halfway down to the subdominant, mirroring the mediant. The last note, 7, is the leading tone, a half step under the tonic. Its name describes what it does: it leads up to the tonic.

Why the leading tone pulls

Play C major up to B and stop. Most listeners feel the tune hanging in the air and want to hear C. The half step from 7 to 1 is the smallest step in the scale, and it ends on the most stable note, so the pull is strong. Many melodies end with ti to do, or re to do, for this reason. In natural minor the seventh note is a whole step below the tonic and has less pull; it gets its own name, the subtonic, which the minor-scale unit comes back to.

Degrees also make it easy to move a tune to another key. "Twinkle, Twinkle, Little Star" starts 1-1-5-5-6-6-5. In C major that is C, C, G, G, A, A, G; in F major it becomes F, F, C, C, D, D, C. The numbers stay put and only the key changes, which is exactly what a singer does when a song is too high and the pianist plays it lower.