PERIODs

A typical period is made of two successive phrases of which the first one ends with a weaker cadence than the second one. The first phrase is called an antecedent phrase while the second one is called a consequent phrase. The antecedent and consequent phrases usually have the same beginnings and different endings. The antecedent phrase usually has a half cadence at its ending. This half cadence calls for a continuation of music. On the other hand, the consequent phrase usually has an authentic cadence at its ending. This authentic cadence creates a sense of resolution.  Half cadences and authentic cadences are explained in chapters: Half cadences and Authentic cadences.   

As an example of the period, we can examine the beginning of the third movement from Mozart’s Piano sonata in C major K. 545. The next figure shows the period i.e. the antecedent phrase and the consequent phrase. We can recognize the half cadence at the end of the antecedent phrase and the perfect authentic cadence at the end of the consequent phrase.

Figure: An example of the period from Mozart's Piano sonata in C major K. 545

A period can have more than two phrases. In such a case, there are more than one antecedent phrase and/or more than one consequent phrase. Consequent phrases must have stronger cadences than antecedent phrases. 

Two or more phrases that seem to belong together but do not form a period are called a phrase group.