CHAPTER XV
Terms Relating to Forms and Styles (Continued)
(Sections [144] to [160] relate particularly to terms used in descriptions of monophonic music[33].)
[144.] A phrase is a short musical thought (at least two measures in length) closing with either a complete or an incomplete cadence. The typical phrase is four measures long. The two-measure phrase is often called section. The word phrase as used in music terminology corresponds with the same word as used in language study.
145. A period is a little piece of music typically eight measures long, either complete in itself or forming one of the clearly defined divisions of a larger form. The period (when complete in itself) is the smallest monophonic form.
The essential characteristic of the regular period is the fact that it usually consists of two balanced phrases (often called antecedent and consequent or thesis and antithesis), the first phrase giving rise to the feeling of incompleteness (by means of a cadence in another key, deceptive cadence, etc.,) the second phrase giving the effect of completeness by means of a definite cadence at the close.
The second half of the period is sometimes a literal repetition of the first half, in all respects except the cadence, but in many cases too it is a repetition of only one of the elements—rhythm, intervals, or general outline. Figs. 58 and 59 show examples of both types. The principle almost invariably holds that the simpler the music (cf. folk-tunes) the more obvious the form of the period, while the more complex the music, the less regular the period.