Two notes are written in the counterpoint to one of the cantus firmus, except in the last measure. [[Fig. 18a].] In the last measure but one the first species may sometimes be used. [[Fig. 18b].]
| Fig. 18. |
Repetition of a note in any but the first species is forbidden. [[Fig. 19.]]
| Fig. 19. |
The counterpoint may begin on the first or the second half of the measure, preference being given to the second half. When it begins on the first half it must be a unison, fifth, or octave; when on the second half, it may be any consonance. [[Fig. 20.]]
| Fig. 20. |
After the first measure the interval on the first beat should be an imperfect consonance, as in the first species, but the fifth, or octave, may be used occasionally.
In this and succeeding lessons, all notes in the measure not belonging to the harmony implied on the first beat, must be treated as dissonances, e.g., those belonging to the implied harmony may be left by a skip (a) or stepwise progression (b) unless dissonant with the cantus firmus; then avoid their use; if foreign to it, whether consonant (c) with the C.F. or not (d), they must be treated as embellishments or passing-tones. [[Fig. 21.]]
| Fig. 21. |
The embellishment may be used as follows: when above the principal tone, it may be a semitone (a) or a whole tone (b) distant from it; and when below, a semitone (c). [[Fig. 22.]]