In using the ninth of a chord it is well to keep it at least a seventh distant from the third, as well as a ninth above the root, except in the case of the dominant ninth in minor keys, where it may be separated by only an augmented second (). [[Fig. 111.]]
| Fig. 111. |
In writing the third species in all parts, notes appearing simultaneously should be harmonically related. Treat all tones foreign to the chord on the first quarter as dissonances.
The cadences in [Fig. 112] are good.
| Fig. 112. |
EXERCISES
To cantus firmus a write third species in one part, as previously directed.
To cantus firmus b write third species in two parts, as in [Fig. 110b]. Write twice, changing the cantus firmus about.
Write one eight-measure phrase, mixing first and third species as in [Fig. 110a].