The Unity Theory of Phrasing
The classical music theory of phrasing is sort of like Kant’s theory of cognition. It’s all about making a unity of a given manifold – in this case a manifold of notes instead of pure intuition.
There is a difference between playing a series of four notes as a series of four notes, and playing them as a four-note phrase. It’s why you’ll hear a difference between a human player and a midi-rendition of the same four-note passage. The difference has to do with adjustments that the human player makes to the sound across a variety of dimensions – timbre, note entry, note length, volume, etc… There are ways to adjust these dimensions that make the four note passage sound like a single four-note phrase, and ways that make it sound less-so. The adjustment of these dimensions, for the sake of making them a unity, is the art of phrasing or interpretation. (I talk about it here).
Phrasing is actually very difficult to learn. Classical music teachers talk about drawing “lines” between notes – essentially varying the aforementioned dimensions in such a way that mentally helps the listener to connect the notes together such that they present as a unity. One easy way to do this is to actually slur the notes together (play them without a bit of silence in between, and minimizing any sonic changes in the transition between the notes, aside from their pitch). Another method involves creating a progression from one note to another note – for instance, playing a sequence of four notes with the first one the softest, and then increasing on each one until you arrive at the last loudest note. These are very basic ways in which to unify notes together by way of phrasing, but even mastering these techniques is quite difficult and takes a number of years to accomplish. I mean this in all seriousness, if you give your standard pop, rock (or even jazz) musician a four bar passage, they will have difficulty playing the notes together as a unified phrase.
More highly attuned classical musicians will employ what I’ll call emotion-mimicking to help bring unity to a series of notes. When people express emotion, these expressions are naturally accompanied by certain types of timbre and cadence. These natural patterns of expression can be employed in interpreting a phrase, given that the melody allows for it. Of course, a standard pop musician will oftentimes invoke what I’ve called emotion-tics, which are essentially the same sort of idea. Though, your standard pop musician (and your standard public speaker) will generally employ only a small handful of emotion-tics, and then beat them to death in an outing. A very skilled musician will have enough control over their instrument to be able to mimic and employ a very large set of emotion-tics.
Beyond emotion-mimicking, skilled musicians will also employ the concept of narrative. Narrative might be something that seems most at home in the domain of the singer-songwriter, since they can directly write a narrative to the melody that they are singing. But, in fact, classical instrumental musicians oftentimes will use narrative in structuring how they interpret and unify the notes of a piece – putting a series of emotions together (by way of emotion-mimicking) into a coherent pattern that suggests a possible narrative.
It goes without saying (or actually not). But every small phrase is itself part of a bigger passage – a four measure passage (let’s say). And every four measure passage is itself part of a section. And every group of sections constitutes a song. And so all of the above techniques are applied on a larger scale to bring unity to a piece. That, in a nutshell, is the unity theory of phrasing.