Categorizing music by form, is hierarchical in nature.

At the smallest usable scale is the motive or motif. The motive is usually a few beats, and gives you small characteristic atoms of music to play with.

At the next size up, is a two measure segment called an idea. This is a technical term. That brings us to phrases.

A phrase in music, is a four measure segment, made up two ideas.

There are different ways of writing your phrases, and they combine into different kinds of larger 8 and 16 measure themes.

Keep in mind, the term phrase in music can mean several different things, depending on what theoretical lens you are looking through. Any definition of a phrase is just a metaphor, and often definitions fall flat of the great amount of ways you can create phrases in music.

So why care about musical phrases? Because they are the vehicle that we will use to unlock our latent creativity. Understanding their use will allow you to write your music with a new sense of clarity and fluency that may have been lacking before.

Theme Types and Musical Phrases

A small musical phrase on its own, doesn’t mean much. It has to be combined with other musical phrases. No one ever said, “I did it! I finally composed Phrase No. 1!” The phrase is just a part of the big picture. The next step in the big picture is the Theme. Let’s examine the most important theme types: Sentence, Period, Small Binary and Small Ternary. They all share commonalities, but they also have some striking differences. For an in-depth discussion of this, check out Classical Form: A Theory of Formal Functions for the Instrumental Music of Haydn, Mozart, and Beethoven, by William Caplin. In this post, we’ll take a look at the Sentence, and then few posts, we’ll follow up with the Period, Small Binary and Small Ternary.

The Sentence

What is a musical sentence? In its most simplest sense, the musical sentence is an 8 measure theme, that consists of two different phrases. Each phrase accomplishes different formal functions. The overall purpose of a sentence is to help establish a tonality and to present the basic material that a composition is made of. The music sentence is a vehicle for presenting your ideas. It accomplishes the “formal functions” of presentation, continuation and cadential.

The archetypal sentence, consists of two, 4 bar phrases. These are the presentation phrase, and continuation phrase. Contained within the continuation phrase, is the cadence.

The Presentation Phrase

This musical phrase normally establishes the tonic, or the home key. It states a basic idea. This basic idea can have any number of motives, but you don’t want to overwhelm your listeners with confusion, so normally you will have one or two motives at most. After the basic idea is stated, it is normally repeated. In order for this repetition to establish the home key better, it will have to fall into one of three categories: exact, statement-response, or model-sequence.

Exact Repetition

This is just as it sounds. You have an exact copy of the basic idea.

Model-Sequence

This type of repetition is usually transposition of the melody up or down in diatonic sequence. It is called model sequence because the first statement is considered the model, the second – the sequence.

Statement-Response

This is probably the most common type of repetition in a sentence, especially an opening sentence. The basic idea is stated, and although is a fully contained unit, it has a force that wants to continue. Stating the basic idea in tonic, the best way to move it along and establish the home key even more, is to restate the basic idea in dominant. Normally, the melody only changes enough to fit the new harmony, and is not drastically changed in terms of where it sits on the staff or range. This also gives the sense of a response to the first statement. Let’s also continue on with the rest of the sentence.

 Continuation Phrase

After the presentation phrase, we follow up the music sentence with a continuation phrase. The continuation phrase can have the same types of repetition as the presentation phrase, but it also has some other unique characteristics. These are: Harmonic Acceleration, Fragmentation, Liquidation and a Cadential Idea.

Harmonic Acceleration

This is speeding up the time change of the underlying harmony. In the presentation phrase, the harmonic speed is one chord for two bars. In the continuation it starts as one chord per bar, and then speeds up in bar 7 to two chords per bar.

Fragmentation

This is basically what it sounds like. You break up the basic idea into smaller fragments, usually one of the unique motives. You can use this for the repetition.

Liquidation

If you take a look at bar 7, you’ll notice that the melody starts to get very simple, leading into two half-notes. This is called liquidation, and it is “stripping away” the uniqueness of the melody and simplifying it.

Cadential Idea

This is basically ending your theme with a cadence. In this case, I chose to leave it open with a half-cadence. Normally you would not end your first sentence on an authentic cadence, unless you had a half-cadence within the presentation phrase.

Put It All Together, and You Got Yourself a Musical Stew

That pretty much covers the sentence. Listen to the complete sentence one more time, but this time, close your eyes, and see if you can hear the different parts. Its a good test. If you have trouble, check out the review of terms below.

Review:

In this post, we introduced the idea of musical phrases being the basis of the basic theme types:

1. Sentence
2. Period
3. Small Binary
4. Small Ternary