I've read a bunch of books and websites on florid counterpoint in 2-4 parts, but it seems like, while there are tons of rules for deciding which tones are okay in which context, very little has been said about which rhythms are appropriate when and in which contexts. Do you know of any resources that discuss choosing rhythms with the same rigor as the topic of choosing pitches is approached?
Piston (among others) writes about this in book simply named "counterpoint". Not sure how much he adheres to Palestrinas counterpoint though...
Some (very) general rules of thumb to get you going are (Besides rhythm accomplished through dynamic accent):
- Notes played on the first, and/or uneven beats of the pulse are considered strong (downbeat). Notes played on even beats of pulse are considered weaker (upbeat).
- Forward rhythmical motion can be expressed through the shifting of strong and weak beats/accents.
- Longer notes tend to carry more accent than shorter notes.
- Notes approached by intervals of a third or larger (leap) tend to accentuate, and vice versa (step).
- Appogiaturas tend to accentuate as well, i.e. using a leap resolving into a step.
- Interesting effects can be caused by one voice following a regular rhythm, while a countermelody varies its rhythmic composition.
- Dissonant harmonies can be used as a mean to accentuate, compared to consonant more smooth harmonies.
There's more to this, and Piston go further into depth in his book.