For this very reason it cannot justly be called "period" at all, but takes the name of "phrase-group." An illustration by diagram will make the distinction clear:-- [Illustration: Phrase group diagram.] Observe that the classification depends upon the number of phrases,--upon the _melodic_ identity of the phrases,--and upon the _quality of the cadences_.
No.

1 is illustrated in Ex.

15; No.

2, in Ex.

42 and the first four measures of Ex.