12. The different degrees of the diatonic scale (§ 9) are known by different names, with which it is necessary that the student should be perfectly familiar, as they are of constant occurrence. The first note of the scale is called the Tonic, or KEY-NOTE. This is the note which gives its name to the scale and key. The scales in § 9, for instance, are the scales of C major and C minor, and it will be seen that they both begin with the note C. The term "tonic" is used in harmony much more frequently than "key-note." The most important note in a key after the tonic is the fifth note of the scale. For this reason it is called the Dominant, or ruling note of the key. The fourth note of the scale lies at the same distance below the tonic that the fifth note lies above it. This will be seen at once by beginning at the top of the scale and descending. This fourth note is therefore called the Subdominant, or lower dominant. We have now got appropriate names for three of the chief notes in the key.
13. About midway between tonic and dominant lies the third note of the scale. We shall see presently that in the major scale it is rather nearer to the dominant, and in the minor rather nearer to the tonic; but, roughly speaking, it is in the middle between the two. It is therefore called the Mediant, that is, the middle note. The sixth degree of the scale lies midway between the tonic and subdominant, just as the third lies between tonic and dominant. We therefore call this sixth note the Submediant, or lower mediant. Some writers on harmony call this note the "Superdominant," or note above the dominant; but the name Submediant is much more usual, and in every way preferable. The second note of the scale is called the Supertonic, i.e., the note above the tonic ; and the seventh note of the scale, which, it will be seen later, has a very strong tendency to lead up, or rise to the tonic is on that account called the Leading Note. It is sometimes, though rarely, called the 'Subtonic,' from its position as the next note below the tonic.
14. Having shown the origin and meaning of these different names, we will now tabulate them.
| First Degree of the Scale | = | Tonic (Key-note). |
| Second " " | = | Supertonic. |
| Third " " | = | Mediant. |
| Fourth " " | = | Subdominant. |
| Fifth " " | = | Dominant. |
| Sixth " " | = | Submediant (Superdominant). |
| Seventh " " | = | Leading Note (Subtonic). |
15. Before proceeding to treat of the names and classification of Intervals, it will be needful to define and explain two terms which we shall very frequently have to use in speaking of them. These are the terms Consonance and Dissonance.
16. A consonant interval, or Consonance, is a combination of two sounds, which by itself produces a more or less complete and
