Unit 3: Periods, Sentences, and Motives; Sequences

Topic 1: Subphrases, Periods, Sentences, and Motives

 Periods

Period—two or more phrases in succession that form a single musical unit because the last phrase’s cadence is more conclusive than the preceding cadence(s).  Note: it can also mean a single phrase ending in a PAC.  The issue is closure; a unit that ends conclusively is a period.

A period usually consists of two phrases, an antecedent and a consequent. If the antecedent is a question (?), the consequent is the answer (.).

Periods We Are Most Likely to Encounter
A period has two main aspects: the degree of similarity between its melodies and its harmonic plan, with a focus on the cadences.  Similar melodic material may help phrases sound like a unit, but this is not necessary in order for phrases to form a period.  The main thing is that the period reserves its most conclusive cadence for the end.

  1. Melodic types
    Parallel:  The phrases’ melodies begin similarly or in exactly the same way.
    Contrasting
    :  The phrases’ melodies differ significantly.
  1. Harmonic plans
    Interrupted
    The antecedent ends with a HC or an AC in V; the consequent begins back on the tonic harmony and ends with an AC.                                                         Continuous:  The antecedent ends with a HC, or with a cadence in a new key.  The consequent does not begin with tonic; and it ends with an AC.
    Sectional
    :  The antecedent ends with an IAC; the consequent ends with a PAC.

    Progressive:  The consequent modulates and ends with an AC in a new key.

Three- and Four-Phrase Periods
Some periods have more than two phrases.

Asymmetrical periods—three-phrase periods
Double periods—four-phrase periods

Double periods often divide into two pairs of phrases on the basis of melodic repetition: a1 b1; a1 b2.  That creates a parallel double period.  The first two phrases form a large-scale antecedent, and the second two form a large-scale consequent.  Here is a typical harmonic plan: IAC HC; IAC PAC.  This an interrupted or a continuous period, depending on whether the second half (phrase 3) begins back on tonic or begins with another chord.

Listening to Periods
The distinctions used for characterizing periods (and larger sections of music, as well) depend on two aural skills:

  1. Hear whether melodic material returns, perhaps in varied form.
  2. Identify the cadences.

To distinguish between interrupted and continuous periods, one must also distinguish between phrases that begin on the tonic chord or on some other harmony.

 Periods and Sentences, with application to “Christ the Lord is Risen Today”

Christ the Lord is Risen Today, alternative interpretation

Analysis of Haydn, String Quartet in E-flat major, Op. 76, No. 6

Analysis of Mozart, Piano Sonata, K. 576

Analysis of Chopin, Grand Valse Brilliante in A minor

 

 

Topic 2: Diatonic Sequences

Sequence – the statement of a pattern two or more times in a row, with each new statement of the pattern being a consistent, generic interval (2nd, 3rd, etc.) higher or lower than the previous one.

  Sequences Defined

A complete label has three parts.  To begin, identify the repeated pattern–the pattern being sequenced.  I like to box or bracket each occurrence of the pattern in the score.  Then

  1. provide the interval of restatement—the interval between one statement of the pattern and the next,
  2. provide the root motion from chord to chord in parentheses, and
  3. note the types of chords using figures.

Most sequences have patterns comprised of just two chords.  That means that there are two figures to record for a sequence, although one of them is often blank, thus representing a root-position triad.

Instead of complete labels, we may also use a shorthand involving the conventional labels shown in the table below.  A shorthand label consists of a conventional label followed by the figures (eg. ↓5, 6).

  Labeling Sequences

  Sequence Types

* Chordal 7ths can be added to descending fifths sequences:
↓5 (7th chords), ↓5 (alternating 7ths), ↓5 (alternating 65’s), and ↓5 (65 and 42’s) are all common.

Identifying Sequences Quickly


 

5 thoughts on “Unit 3: Periods, Sentences, and Motives; Sequences

  1. THANKS! My AP Theory class was struggling with the sentence. Your explanation is terrific. Many thanks –

    Tammy Grant
    University School of Jackson

  2. Great resource, but I came looking for an answer that your heading implies it’s going to address. The heading says sentences will be discussed, and then they’re not. They’re not covered in the video, either. I’m trying to figure out the relationship between sentences and periods. I’d also like to know if all “good” compositions are completely comprised of periods and sentences, or if there’s just some “free” material out there. I’d like to know how phrases fit in with sentences. I’m gathering that not all sentences are periods, but all periods are comprised of sentences, and phrases are the building blocks of sentences (and, thereby, building blocks of periods). Do I have that right?

    • Hi Chris.

      These pages are definitely a work in progress. I’ll try to answer your questions in this reply.

      Periods are defined by closure. They almost always ending with a perfect authentic cadence, and any preceding cadences within the period are less conclusive than the final cadence. That is why the phrases are said to join together as one period.

      Sentences are melodic and durational patterns, primarily. There is a basic idea, or motive, that is repeated or sequenced, perhaps with variation. Then there is the continuation, which may or may not be related to the basic idea, but which is twice the length of the basic idea.

      Unlike periods, sentences do not have to have a particular degree of closure. That allows them to be present at several levels of phrase structure. Sub-phrases, phrases, periods, and even whole pieces (witness “bar form,” which is sentence structure at the level of the whole piece) can be sentences. In fact the continuation of a large sentence may itself be a sentence. If the large sentence is a phrase, the smaller sentence within its continuation is a sub-phrase. If the large sentence is a period, the smaller sentence within its continuation is likely a phrase.

      Movements consist of nothing but periods, almost by definition. If the movement ends in a PAC, there is at least one period. Some pieces and movements have many sentences, but there is often material that does not belong to a sentence.

      Hoping that helps,
      Austin

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