Identifying Period Type

Question

I've attached a music excerpt that's been stumping me. Is the attached passage a parallel period or a contrasting period? The rhythmic repetition makes it seem parallel, but the chord progression and melody seem contrasting.

Answer 1

TL;DR

With allowance for the interpretive aspect of music analysis ...

I would label this a parallel period.

The ambiguity

The problem, of course, lies in the ambiguity in the definitions of parallel and contrasting periods. For example:

In a parallel period, the melodies in both phrases begin similarly. In a contrasting period, the phrases begin differently. (Source: Music Theory for the 21st-Century Classroom by Robert Hutchinson, "13.3.4 Parallel and Contrasting Periods")

This is easy when the parallel phrases begin identically, which is often the case. However, the definition doesn't explain how similar or how contrasting. Thus, the answer depends on how heavily one weighs the parallel aspects of the phrase against the contrasting ones.

Interpretation

Here's my own informal definition.

In a parallel period, the consequent phrase begin such that the listener is likely to recall or associate it with the antecedent. In a contrasting period, the consequent phrase is intended to present a wholly new idea.

For my own purposes, at least, this way of looking at it makes the phrase in question parallel. Even with the harmonic contrast, the rhythm is enough to bring the listener clearly back to the antecedent phrase, which I interpret as the composer's intent. I would expect a contrasting phrase to be "more contrasting" than this one.

Opposing view

My own definition could be used to make the opposite point. Given the harmonic change, perhaps the composer's intent is to highlight the contrast between the two phrases — specifically by adding just enough parallelism to reference the antecedent phrase, but not enough to make the phrases "genuinely" parallel.

This again comes back to the idea that the label depends on the interpreter's prioritization of the parallel aspects versus the contrasting ones. I give more weight to the parallel in this particular case (though reserve the right to analyze another seemingly similar phrase differently). But an interpreter giving more weight to the contrast wouldn't be wrong.

... And thus begins many a debate among music theorists.

The ultimate test

When in doubt, listen to the passage. This is the essential arbiter of music theory questions: how do you, the theorist, hear the passage. If the antecedent phrase recalls for you the consequent, it's parallel; if the antecedent phrase sounds like it's own entity, then it's contrasting.