In prose, this syncopation is evident in the apparent recognition, and even reproduction in reading aloud, of a regularity of rhythm where none really exists; as when protracted reading or listening develops or seems to develop a monotonous sing-song. But this phenomenon cannot be explained briefly, and the details must be omitted here.[11] In verse also syncopation frequently occurs, though it is seldom recognized except as an 'irregularity.' In the following lines of Paradise Lost the first two coincide pretty closely with the normal beats of the measure; while in the third line the series is an entirely different one.
So Satan spake, and him Beelzebub
Thus answered: "Leader of those armies bright,
Which but th' Omnipotent none could have foil'd...."
Milton, Paradise Lost, I, 271-273.
Here to stress distinctly but,-tent, could utterly ruins both the meaning and the music of the line: to utter the words as if they were ordinary prose would preserve the meaning, but destroy the verse-movement. In Milton's ear, however, and in ours if we do not resist, there is a subtle syncopation of four beats against five. (Of course syncopation alone does not explain the rhythm of this line.) A most startling syncopation is ventured by Milton in Samson Agonistes (1071-72):
I less conjecture than when first I saw
The sumptuous Dálila floating this way.
Substitution is simpler. It merely means recognizing the equivalence, and therefore the possibility of interchange, of a long interval with two or more shorter intervals whose sum equals the one long. That is, in music two quarter-notes are equal to a half-note, and they may be anywhere substituted one for the other; or a dotted half-note equal three quarter-notes, etc. In verse it means that three syllables (or one, or even four) may be substituted for the normal two syllables of a foot if the three (or one or four) are uttered in approximately the same period of time.
The term substitution, however, may be used in a larger sense. Thus far only the purely temporal element of the rhythm has been thought of. When the two others, stress and pitch, are recalled, it becomes clear that another sort of substitution is both possible and usual, namely, that of either pitch or stress for duration. In other words, the groups that make up a rhythmic series may be determined or marked off by emphasis of pitch or emphasis of stress as well as by duration of time. In fact, it is from this habitual interplay of the three elements that most of the complexity of metre arises; as it is the failure to recognize this substitution which has given the older prosodies much of their false simplicity and their mechanical barrenness.
Summary. The fundamental problems of versification are all involved in the principles of rhythm, especially the temporal rhythm of language. The rhythm of both prose and verse is a resultant of the three attributes of sound: stress, duration, and pitch (the first two being usually the determining elements, the third an accessory element) modified by the thought and emotion of the words. The feeling for this rhythm, or perception of it, has both physical and psychological explanations, and varies considerably among individuals, some being 'timers,' others 'stressers,' apparently by natural endowment. The processes of our perception of rhythm are those of coordination, or partly subjective reduction of actual 'irregularities' to a standard of 'regularity'; this reduction being accomplished mainly by syncopation and substitution.