Phrase Structure and Motivic Analysis

• Motives are labeled with numbers or lowercase letters from the end of the alphabet
• The letters at the beginning of the alphabet are reserved for phrases and larger units
• Motives can be named descriptively: the arpeggiated motive, the neighbor-note motive, the dotted motive, the descending-thirds motive, the extended scale motive

Variation of Motives

Variety is a spice of life; this is true, especially in music. Motives can be changed up in a few different ways:

• Transposition occurs when a motive appears on another scale degree
• Inversion occurs when the direction of each diatonic interval is reversed ( keep the order of interval sizes the same, but reverse each interval in direction, e.g. an ascending third becomes a descending third)
• Extension occurs through repetition of a portion of a motive to make it longer
• Truncation occurs when the motive is made shorter by removing a portion from the end
• Fragmentation occurs when a small, yet recognizable, portion of the original motive is repeated with any of the other methods of variation listed above

The Sentence

A sentence is usually an 8 or 4 bar unit with the smaller units – subphrases – divided in bars as 2 + 2 + 4 or 1 + 1 + 2, respectively. The first two units do not end with a cadence, but the third unit brings a sense of closure to the phrase.

A motive – the basic idea – is stated in the first unit and is usually over the tonic harmony. The motive is restated in the second unit; it may be identical to the first statement, but it is usually varied or transposed. This restatement is usually over a dominant harmony or a tonic expansion. These first two units are called the presentation. Finally, in the third unit, the motive is decomposed and developed with a faster harmonic rhythm, that moves toward the cadence – often a half cadence or perfect authentic cadence. This final unit is called the continuation.

The term “sentence,” is reserved for cases where the presentation phase is harmonically incomplete, and the true cadence is only found in the continuation.

The Period

Periods are formed when there are two phrases – one with a harmonically weak cadence and the other with a stronger cadence. The first cadence is usually a half cadence or inauthentic cadence, while the second is usually a perfect authentic cadence. The first phrase is called the antecedent and the second is called the consequent.

Phrases in a period can be symmetrical – both phrases would be the same length – or the phrases can be asymmetrical with both phrases being different lengths.

Sentences may be embedded in periods.

• Parallel Period (a a or a a’)
• Contrasting Period (a b)
• Modulating Period (changes keys)
• Three-phase Period (a a b, a b b’, a b a’ or a b c)
• Double Period (a b a’ b’)

Phrase Rhythm

Phrase Structure and Hypermeter

An understanding of motives, phrases, sentences, and periods allows us to give a musical line direction and perform it without sounding choppy and amateurish.

To find the rhythm and flow of a piece you basically have have two strategies:

One approach is harmonic: locate the cadences, then move through the harmonies in th emiddle of th phrase toward the harmonic goal. The other, a metric strategy, requires you to focus on larger hepermetric levels.

The Musician’s Guide to Theory and Analysis, Third Edition, p. 377

Hypermeter interprets groups of measures as beats within a single measure. The way hypermetric structure and phrase structure align is known as phrase rhythm. When you understand the relationship between hypermeter and phrase structure you can then begin to treat phrases as though they were one bar like successive waves of sound washing over the listeners.