Parallel motion

What do you consider as the pros and cons of using full parallel motion in harmony (or just two voice counterpoint)? As a temporary effect, of course, not as the main voice leading principle of a whole piece.

I find myself often using partial parallel motion, with one interval moving against other(s) in parallel motion, or using chords moving in parallel in mirror writing against each other (-- at this point i wish it was easier to post examples).

I think it sounds great as an exclamation mark of sorts, but then again, parallel motion is not something you'd get praised for in the composition class. :)

the only real issue with parallel motion is that it has a strong tendency to remove a sense of individuality of lines.

For example, in species counterpoint lessons, you are generally limited to a fixed number of parallel intervals (3rds and 6ths are the only intervals you may use anyways) because it defeats the purpose of counterpoint - to create individual lines. More than a certain number of parallel intervals in a row does nothing to create a sense of independance of line. I say "a certain number" because it is a variable amount, and depends on both context and the particular school of species counterpoint in which you are training.

I mention in the orchestration masterclass the principle of "thickened melodic line", where other intervals are added in parallel motion. This does not, however, create "real" additional lines. It is merely as the name suggests a thickening of the initial melodic material.

A prime example of "thickened line" is Ravel's Bolero. Much of the actual texture of the piece, even at its most dramatically "loud", is a very simple 2-part texture. The complexity comes from the amount of parallel motion in the thickened lines.

Good answer, thanks. Ravel is of course a most inspiring example of using parallel motion.