Rhythm, in its simplest sense, is measured motion; but by various natural extensions of meaning the word has come to be used almost as a synonym of regularity of variation. Whatever changes or alternates according to a recognizable system is said to be rhythmic, to possess rhythm. In this sense, rhythm is one of the universal principles of nature. We find it in the stripes of the zebra, the indentation of leaves, the series of teeth or of crystals, the curves of the horizon; in the tides, the phases of the moon, the rising and setting of the sun, the recurrence of seasons, the revolutions of planets; in the vibrations of color, sound, and heat; in breathing, the throbbing of the pulse, the stride of walking. All action and reaction whatever is rhythmic, both in nature and in man. "Rhythm is the rule with Nature," said Tyndall; "she abhors uniformity more than she does a vacuum." So deep-rooted, in truth, is this principle, that we imagine it and feel it where it does not exist, as in the clicking of a typewriter. Thus there is both an objective rhythm, which actually exists as rhythm, and a subjective rhythm, which is only the feeling of regularity resulting from a natural tendency of the mind to 'organize' any irregularity that we meet.

There are two fundamental forms of rhythm, though these are not altogether mutually exclusive, (1) spatial, and (2) temporal.

Spatial Rhythms. The simplest spatial rhythm is a series of equidistant points—

..........

More complex forms are the succession of repeated designs in mouldings and wainscotings (for example, the alternation of egg and dart), the series of windows in a wall, or of the columns of a Greek temple, or of the black and white keys of a piano. Still more complex is the balanced arrangement of straight lines and curves in a geometrical design, as in certain Oriental rugs or the Gothic rose windows. And probably the most complex spatial rhythms are those of the facades of great buildings like the Gothic cathedrals or St. Mark's of Venice, where only the trained eye perceives the subtleties of alternation and balance.

Temporal Rhythms. Temporal rhythms, apart from those of planetary motion, the alternation of seasons, and the like (which are called rhythmic by a metaphorical extension of the term), manifest themselves to us as phenomena of sound; hence the two concepts time-rhythm and sound-rhythm are commonly thought of as one and the same.

The simplest form is the tick-tick-tick of a watch or metronome. But such mechanical regularity is comparatively rare, and in general the temporal rhythms are all highly complex composites of sounds and silences. Their highest manifestations are music and language. The rhythm of language, and a fortiori that of verse, is therefore primarily a temporal or sound rhythm, and as such is the particular subject of the following pages.

Combinations. Language, however, when addressed to the eye rather than to the ear, that is, when written or printed rather than spoken, is partly a spatial phenomenon; and, as will appear presently, the arrangement of words and sentences on the formal page is a real factor in the rhythm of verse. Moreover, most of the rhythms of motion, such as walking, the ebb and flow of tides, the breaking of waves on the beach, are composites of temporal and spatial.[1]

Sound Rhythm. These elementary generalizations must be narrowed now to the special phenomena of sound, and then still more particularly to the sounds of language.

All musical tones, including the phonetic sounds of words, have four characteristics: pitch, loudness or intensity, quality or tone-color, and duration. The last, of course, needs no definition.

Pitch is dependent on the number of vibrations per second. The greater the number of vibrations, the higher the pitch and the more 'acute' the tone. The lowest pitch recognizable as a tone (as distinguished from noise) is 8 vibrations a second; the highest pitch the ear can hear is between 20,000 and 30,000 a second. In normal English speech among adults the voice ranges from about 100 to 300 vibrations, but in animated speaking this range is greatly increased.

Loudness is a comparative term for the strength of the sensation of sound in the ear. It is determined by the energy or intensity of the vibrations and varies (technically speaking) as the product of the square of the frequency and the square of the amplitude (I=n²A²). But for ordinary purposes it is sufficient to regard loudness and intensity as the same. The distinction, however, is clear in common practice; for whether one says "father" loudly or quietly, there is a relatively greater intensity of sound in the first syllable than in the second. In speech this intensity is called accent or stress.

The third characteristic, variously called quality, timbre, tone-quality, tone-color, is that which distinguishes sounds of the same loudness and pitch produced by different instruments or voices. It is the result of the combination of the partial tones of a sound, that is, of the fundamental and its overtones. In music, tone-quality is of the utmost importance, but as an element of speech rhythm it is practically non-existent, and may be wholly neglected, though it plays, of course, a prominent part in the oral reading of different persons.[2]

What is the relation of these physical attributes of sound to sound rhythm? The answer lies in a closer examination of the nature of rhythm, especially as it concerns the rhythm of speech.

Rhythm means measured flow or succession. Now first, in order that any succession may be measured, there must be something recognizable which distinguishes one unit from the next. In spatial rhythms the point of division is almost always easily perceived; hence the greater difficulty of analyzing the simplest time-rhythms as compared with the most complex space-rhythms. Moreover, the basis of measurement, that by which the 'distance' between any point of division and that which follows it is determined, must, by definition, be duration of time. Suppose, however, that the time-distance between successive points of emphasis or division is equal, is the rhythm therefore necessarily regular? No, because the points of emphasis themselves may vary in force or energy. Thus if in the following scheme (´ = point of emphasis; - = equal time-distance):

´-´-´-´-´-´- etc.

every ´ is not of the same value, the result might be (´´ = twice as much emphasis as ´; ´´´ = three times as much):

´´-´-´´´-´´-´´´- etc.

and this could not be called regular. A simple illustration of this is the difference in music between 3/4 time, where we count 1´ 2 3, 1´ 2 3, 1´ 2 3 and 6/4 or 6/8 time, where we count 1´´ 2 3 4´ 5 6, 1´´ 2 3 4´ 5 6. Furthermore, apart from any question of force or energy applied in the production of a sound, it is clear that high notes seem to possess a greater strength than low notes, and must therefore be recognized as an element in rhythmic emphasis. For example, if the following series of notes were sounded on a piano, and each struck with equal force—

Musical notes-A E A E A E etc.

a certain 'accent' would probably be felt on the e which was not felt on the a. And it is well known that shrill sounds and high-pitched voices carry farther and seem louder than others.

In the simplest kind of temporal rhythm, therefore, where the beats are, say, drum-taps of equal force, the primary element is time. But if there is the added complication of drum-taps of unequal force, the element of comparative stress must be reckoned with. And if, finally, the drum-taps are not in the same key (say, on kettledrums differently tuned), then the further element of comparative pitch must be considered as a possible point of emphasis. In a word, pitch may sometimes be substituted for stress.

In music rhythmic units may be marked by differences in tone-quality as well, and thus the potential complexity is greatly increased; but in spoken language, as has been said, this element of rhythm is negligible. In speech-rhythm, however, the three conditions of time, stress, and pitch are always present, and therefore no consideration of either prose rhythm or verse can hope to be complete or adequate which neglects any one of them or the possibilities of their permutations and combinations. And it is precisely here that many treatments of the rhythm of language have revealed their weakness: they have excluded pitch usually, and often either stress or time. They have tried to build up a whole system of prosody sometimes on a foundation of stress alone, sometimes of time alone. The reason for this failure is simple, and it is also a warning. Any attempt to reckon with these three forces, each of which is extremely variable, not only among different individuals but in the same person at different times—any attempt to analyze these elements and observe, as well, their mutual influences and combined effects, is bound to result in a complication of details that almost defies expression or comprehension. The danger is as great as the difficulty. But nothing can ever be gained by the sort of simplification which disregards existent and relevant facts. It is to be confessed at once, however, that one cannot hope to answer in any really adequate way all or even most of the questions that arise. The best that can be expected is a thorough recognition of the complexity, together with some recognition of the component difficulties.

Moreover, only a part of the problem has been stated thus far. Not only is all spoken language the resultant of the subjectively variable forces of time, stress, and pitch, but these three forces are themselves subject to and intimately affected by the thought and emotion which they express. Though educated persons probably receive the phenomena of language more frequently through the eye than through the ear, it is true that words are, in the first instance, sounds, of which the printed or written marks are but conventional symbols. And these symbols and the sounds which they represent have other values also, logical or intellectual and emotional values. Language is therefore a compound instrument of both sound and meaning, and speech-rhythm, in its fullest sense, is the composite resultant of the attributes of sound (duration, intensity, and pitch) modified by the logical and emotional content of the words and phrases which they represent.

For example, utter the words: "A house is my fire," and observe the comparative duration of time in the pronunciation of each word, the comparative stress, and the relative pitch (e. g. of a and fire). Now rearrange these nearly meaningless syllables: "My house is afire." Observe the differences, some slight and some well marked, in time, stress, and pitch. Then consider the different emotional coloring this sentence might have and the different results on time, stress, and pitch in utterance, if, say, the house contains all that you hold most precious and there is no chance of rescue; or if, on the other hand, the house is worthless and you are glad to see it destroyed. And even here the matter is comparatively simple; for in reading the following sentence from Walter Pater, note the manifold variations in your own utterance of it at different times and imagine how it would be read by a person of dull sensibilities, by one of keen poetic feeling, and finally by one who recalled its context and on that account could enjoy its fullest richness: "It is the landscape, not of dreams or of fancy, but of places far withdrawn, and hours selected from a thousand with a miracle of finesse."[3]

The last step of the complication, which can only be indicated here, and will be developed in a later chapter, comes with the mutual adjustment of the natural prose rhythm and the metrical pattern of the verse. Such a sentence as the following has its own peculiar rhythms: "And, as imagination bodies forth the forms of things unknown, the poet's pen turns them to shapes, and gives to airy nothing a local habitation and a name." Now read it as verse, and the rhythms are different; both the meaning and the music are enhanced.

These then are the problems and the difficulties. The solutions can be only partial and tentative, but they are the best we are able to obtain with our present knowledge and our present capabilities of analysis. As science today has advanced in accuracy of knowledge and understanding of the facts of nature far beyond the powers of our ancestors to imagine, so in the future psychologists may, and let us hope will, enable us to comprehend the subtleties of metrical rhythm beyond our present power. Yet there will always remain, since the ever-inexplicable element of genius is a necessary part of all art, a portion which no science can describe or analyze.

The Psychology of Rhythm. That nearly all persons have a definite sense of rhythm, though sometimes latent because of defective education, is a familiar fact. The origin and source of this sense is a matter of uncertainty and dispute. The regular beating of the heart, the regular alternation of inhaling and exhaling, the regular motions of walking, all these unconscious or semi-conscious activities of the body have been suggested; and they doubtless have a concomitant if not a direct influence on the rhythmic sense. Certainly there is an intimate relation between the heart action and breath rate and the external stimulus of certain rhythmic forces, as is shown by the tendency of the pulse and breath to adapt their tempo to the beat of fast or slow music. But this can hardly be the whole explanation. More important, from the psychological point of view, is doubtless the alternation of effort and fatigue which characterizes our mental as well as physical actions. A period of concentrated attention is at once followed by a period of indifference; the attention flags, wearies, and must be recuperated by a pause, just as the muscular effort of hand or arm. In truth, the muscles of the eye play a real part in the alternations of effort and rest in reading. The immediate application of this psychological fact to the temporal rhythms has been clearly phrased by the French metrist, M. Verrier:

Thus we have always at hand both a more or less efficient bodily metronome in the pulse and in respiration, and also a "cerebral metronome" capable not only of easy adjustment to different rates of speed but also of that subtlest of modulations which psychologists call the 'elastic unit,' and which musicians, though not so definitely or surely, recognize as tempo rubato.

The sense of rhythm, as has been said, differs remarkably in different individuals—just as the sense of touch, of smell, of hearing.[5] To some, rhythm appears chiefly as a series of points of emphasis or stresses alternating with points of less emphasis or of none at all; such are called, in scientific jargon, 'stressers.' To others the principal characteristic of rhythm is the time intervals; such are called 'timers.' But this is a practical, not a philosophical distinction. For it is the succession of points of emphasis which even the most aggressive stresser feels as rhythmic; and succession implies and involves a temporal element. The stresser's only difficulty is to feel the approximate equality of the interval. The essential thing, however, is to understand that, while time is the foundation of speech-rhythm, stress is its universal adjunct and concomitant.[6]

The explanation of this duality is simple. A series of identical tones

Identical notes etc.

contains a simple objective rhythm. The pronounced timer will feel it clearly; the extreme stresser will not. Change the series to

Alternate long and short notes etc.,

or

Alternate longer stressed notes and shorter unstressed notes etc.,

and both will feel it; for in the last example both time and stress are obvious, and in the other the longer notes of the series produce the effect of stress.[7] Most persons, therefore, with a greater or less degree of consciousness, allow their physical or cerebral metronome to affect the simple

Identical notes etc.,

so that they hear or feel either

Alternate stressed and unstressed notes etc.,

or

musical notation etc.,

It is thus that the clock says tick-tock, tick-tock, the locomotive chu-chu, chu-chu. Timers are in the minority.

A converse phenomenon of the subjective introduction of stress into a series of identical tones at equal intervals is the subjective 'organization' of a series of irregular beats. Some do this more easily and naturally than others, but the tendency is present in all who are not absolutely rhythm-deaf. The "minute drops from off the eaves" beat out a tune, the typewriter develops a monotonous song, the public speaker 'gets his stride' and continues in a sing-song.

Thus, when there are equal intervals but stress is absent, we more or less unconsciously supply it; when there are distinct stresses at irregular intervals we organize them into approximately regular intervals. We have in us by instinct and by development both the ability and also the need to draw forth rhythm wherever it is latent. Rhythm becomes one of our physical and mental pleasures, manifest in primitive dancing and balladry, sailors' chanteys, and the simple heave-ho's of concerted labor. It induces economy of effort, and so makes work lighter; and it has, though perhaps not always, a certain Æsthetic value, in making labor more interesting as well as easier. It is one of the attributes of the god we worship under the name of System.

CoÖrdination, Syncopation, Substitution. The processes of the subjective organization of rhythm may best be explained under the heads of coÖrdination, syncopation, and substitution. Their application to the particular problems of verse will be apparent at once, and will, in fact, constitute the bulk of the following pages.

CoÖrdination has two aspects, according as it is thought of simply as an existing fact or as a process. In the former sense it is the agreement or coincidence (or the perception of agreement or coincidence) between the simple normal recurrence of beats and the actual or predetermined pattern. Thus in the lines

the 'natural' beat of the words uttered in the most natural and reasonable manner coincides with the 'artificial' beat of the metrical line.

On the other hand, coordination is the process which results in one's reduction of irregular beats to an approximately regular series. When we hear a haphazard succession of drum-taps or the irregular click-click of the typewriter, most of us soon begin to feel a certain orderly arrangement, a rhythmical swing in the repeated sounds, a grouping according to a sort of unit which recurs with nearly equal intervals. The units are not absolutely equal, but are elastic, allowing of some contraction and expansion; yet they are so nearly equal, or we feel them so, that the series seems regular.

Now this process of coÖrdination involves two activities, syncopation and substitution. The workings of both are highly complex and somewhat uncertain; they differ greatly in different individuals, and when analyzed scientifically seem to produce more difficulties than they explain. But fortunately the outstanding ideas are beyond dispute, and detailed examination can properly be left to the scientists.

Syncopation is the union, or the perception of the union, of two or more rhythmic patterns.[8] A familiar example is perhaps the 'three against two' in music, where one hand follows a tum-te-te, tum-te-te rhythm, the other a tum-te, tum-te. This complexity, which strikes us as sophisticated subtlety and is not always easy to reproduce, is in fact both simple and familiar to the untutored savage. We must remember that the evolution of language and of music has been for the more part in the direction of greater simplicity of structure. Primitive music, as we find it in the undeveloped Indians and Australasians, is often too complex to be expressed by our regular notation. Another familiar example of syncopation is the negro dance, in which the "dancer taps with his feet just half-way between the hand-claps of those who are accompanying his performance."[9] And of course the commonest example is the strongly marked syncopation of ragtime.[10]

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.

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):

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.