Phrase and period

Melodies are built from phrases subject to certain rules, just like the sentences of spoken language (Med 1996, ch. XLIX). The comparison works well. A spoken sentence has a beginning, a development and punctuation, and two sentences can make a question and its answer. Music is the same.

The phrase

Med defines the phrase as a musical unit with a sense of conclusion. It usually spans four or eight bars and may be made of two or three semiphrases (Med 1996, ch. XLIX).

What marks the end of a phrase is the cadence: the melody reaches a point of rest and hesitates. A phrase can end on an incomplete cadence, which asks to go on, or a complete one, which sounds like an end.

Call and response

One of the oldest ways of organising melody is call and response: a phrase is stated, perhaps by a single voice, and repeated or answered with another phrase, perhaps by a group. Blatter notes that these structures are at least as old as the Psalms, and gives as an example the military drill songs in which the sergeant sings a line and the troops sing it back (Blatter 2007, part 5, art. 2). It is also the logic of responsorial church singing and of much popular music.

Sometimes the response matches the call; sometimes it changes, on purpose, as part of the form (Blatter 2007, part 5, art. 2).

The period: antecedent and consequent

When the first phrase sounds incomplete and the second seems to complete it almost inevitably, the two form a pair of antecedent and consequent (Blatter 2007, part 5, art. 2). Together they make a period, which ends with a conclusive cadence in the second phrase, in a question-and-answer relationship (Med 1996, ch. XLIX).

The antecedent sounds incomplete because it ends on a degree other than the tonic, usually the dominant or the supertonic, making a melodic half cadence. The consequent almost always ends on the tonic, with a complete cadence (Blatter 2007, part 5, art. 2).

An eight-bar period. The antecedent, which stops on D:

Hear the passage

The consequent, which starts the same way and reaches C:

Hear the passage

The identical beginning makes the ear hear the second phrase as an answer to the first; the different ending is the answer itself.

A song phrase by phrase

Blatter analyses "Home on the Range", a traditional American song, phrase by phrase (Blatter 2007, part 5, art. 2):

Phrase	Ends on	Letter
1st, antecedent	supertonic, incomplete	A
2nd, consequent	tonic, complete	A′
3rd, contrasting	supertonic, incomplete	B
4th, same as the 2nd	tonic, complete	A′

The third phrase starts with new material but ends with the familiar tune, and again on the supertonic, which makes the listener expect a fourth, more final phrase (Blatter 2007, part 5, art. 2). It is song form, A A′ B A′.

Balanced phrases

Since the eighteenth century, popular songs, folk songs and many art songs have tended to have balanced phrases, and by far the favourite length is four bars, or at least a multiple of two. Sections of sixteen or thirty-two bars, with phrases of eight or sixteen, are extremely common. A period of two phrases of the same length has balanced phrases (Blatter 2007, part 5, art. 2).

That is why a listener, without counting, feels when a phrase "should" end. And that very expectation is what a composer can defy.

Shorten, lengthen, dovetail

To avoid monotony, or to create surprise, drama or humour, many composers break the balance on purpose (Blatter 2007, part 5, art. 2).

Truncated phrase. The phrase is cut short of its expected length. The consequent above, without its second bar, reaches the tonic too soon:

Hear the passage

Prolonged phrase. The phrase is lengthened beyond what is expected, by repeating material, a motive for instance, or by adding new material before the cadence (Blatter 2007, part 5, art. 2).

Elided phrases. The end of one phrase is at the same time the beginning of the next: the note the first phrase lands on is already the first note of the other (Blatter 2007, part 5, art. 2).

All three devices work best once the listener is used to balanced phrases, because the effect comes from the broken expectation.

Phrasing

Med calls phrasing the art of making the beginning and end of each phrase evident through accentuation (Med 1996, ch. XLIX). In the score, phrasing sometimes appears as a long curved line over the phrase; in performance, it is the singer's breath, the bow stroke, the small gap before the next phrase.

Med also notes that every melody should have a lowest and a highest point, its culminating points, and that the high one is often near the end (Med 1996, ch. XLIX). In the period above, the lowest point, middle C, is in the antecedent; the highest, the E, comes in the consequent, two bars before the end.

What comes next

Phrases and periods join into sections, and sections into forms: binary, ternary, song form. And when there are words, the musical phrase and the phrase of the text have to line up.