RHYTHM IN MUSIC Like all artistic categories musical rhythm must be studied his torically, to avoid Philistinism towards the rhythms of early periods. But the musical rhythms of the i8th and i9th centuries are so much more familiar to us than any others, and so radically different from speech-rhythms, that we shall do well to analyse them first. Their true relation to speech-rhythms will then become much clearer, and the study of older rhythms will be greatly simplified.
I. Body-rhythm and Speech-rhythm.—These are two pre historic elements in musical rhythm ; and in modern music they are in equipoise, though apart from music they are incompatible. Dance-rhythm is too narrow a term for the one, and speech rhythm is a satisfactory term for the other. We may coin the term body-rhythm as giving the necessary extension to the notion of dance-rhythm. Musical body-rhythm, even in the slowest paces, is enormously stronger than anything known to prosody. It is no exaggeration to say that it is as strong as the pace of a horse. Not even Browning could have recited "How they brought the good news from Ghent to Aix" with comfort while riding a galloping horse; but Schubert's Characteristic Marches (op. I 2I ) do not merely imitate that pace but go far to stimylate it if played to a body of cavalry. Gentler rhythms may be less immediately understood, but, once grasped, are not more easily changed. The music must brace itself up for any abrupt change of its funda mental rhythm. But that fundamental rhythm may be very slow and lie very deep.
In the example on p. 274 (Ex. I), Haydn uses an underlying rhythm of thrice two beats. The beat is a quaver, for which one second is not too slow a tempo for this particular composition. Its whole group of six beats is invariably 3 and never 2 ÷ 3. In this kind of music change from the one division to the other would be impossible without either violence or vagueness ; unless it were a permanent change of metre. So important is the notion of 34-2 that it is not counted as 6 at all, but as 1 & 2 & 3, etc. Of
these beats the first bears the chief stress, the second and third bear less, and there is no rule to give either more stress than the other. We are not, at present, considering the case of three beats quick enough to mark the rhythm without subdivision. Obviously the subdivisions (counted by "&") have no accent, except in rela tion to their own further subdivisions. Musical rhythms are measured from accent to accent and of pairs of accents the first is stronger than the second. In larger groups, if the rhythm is binary the third accent will be stronger than the second, but not as strong as the first or fifth. At a very quick pace the difference of strength between the first accent and the fifth may become per ceptible, but the rhythm would be inartistically stiff if such dis tinctions were not soon obliterated.
Triple rhythm, whether slow and subdivided or quick and un divided, also falls readily into larger binary periods with the same relative strengths of accent. There is nothing to prevent it from falling into ternary periods, but the mind ceases to apprehend a high power of three rhythmically, for we cannot know that the third period of a slow group is not the first of a new pair.
On these data it is now possible to analyse the rhythm of Ex. I. It begins on the main accent, with no anacrusis. Between the first and second quaver beats there is a group of grace-notes. In actual time these should come on the second quaver and reduce the length of the second main note instead of that of the first, but they have no accent, and the second main note has its due stress and is not noticed to have arrived late, even if the grace-notes have been taken with some deliberation. They are like the con sonants in the word three: it is easy to pronounce the word at a given moment, and nobody thinks of dividing it as three, though the consonants really take an appreciable time.