Rules For Second Species of Strict Counterpoint in Two Parts.
In the Second Species two notes of C.P. are written to each note of the C.F.
I. The second note in the measure may be a Dissonant (Passing Note), provided it is taken and left, in one of the three ways following:
1st. As the middle note of three notes ascending or descending diatonically.
2nd. As the middle note of three, the first and third of which are the same, and the middle one is the degree above or below.
3rd. When the dissonant note enters one degree above a consonant and falls a third to the next consonant.
II. Never begin two successive measures with Eighth, Fifth or Unison.
III. The C.P. should begin with a half-rest, and the first note of the C.P. must be consonant (see Rule II, first species). The final must be a whole note.
IV. Avoid leaps in the C.P. as much as possible; the more passing notes, the better the C.P.
It is permitted to let the parts cross for a few notes, but it is better to avoid it in two-part C.P. The following are considered the best endings:
It is sometimes permitted to write a dissonance at the beginning of a measure for the sake of preserving a smooth movement in the C.P.
Example. C.P. above.