To the principles of beauty belong, above all things, order and
regularity. In music this order consists in measures of time. All
measurement by time, even the scientific, depends upon rhythmic,
regularly returning results, as in the revolutions of the earth,
of the moon, and in the vibrations of the pendulum, &c. Thus, by
the regular interchange of accented and unaccented sounds in
music and poetry, we obtain the rhythm of the work.
But while in poetry the structure of verse serves only to
reduce to artistic order the external accidents of expression
by language, rhythm is not only the external measure of time in
music, but it belongs to the innermost nature of its power of
expression, giving to music its distinctive character. There
is, therefore, a finer and much more various culture of rhythm
necessary in music than in poetry. Here rhythm determines not
only the time, how long a note is to be maintained, and how
many notes fall within a certain space of time, but it also
distinguishes those notes which are to be sung with more or
less emphasis.
We know that in a bar of 2/4 time the first beat must be more
accented than the second; in a bar of 4/4 time the rhythmical
accent falls upon the first and third beats; in a bar of 3/4 and
3/8 time only upon the first; and in 6/8 upon the first and
fourth. This rhythmical accentuation must become a second nature
to the learner before he can express any particular sentiment in
a piece of music, and therefore he must be early practised in it.
Rhythmical accentuation can always be employed very differently
according to the character (_Stimmung_) of a composition, and the
most different effects in expression are thus produced. One can,
by a greater or less degree of strength, or by a sudden impulse
of the breath, change the accent, as well as by a slight
retardation of the note. Also, by transferring the accent to
those notes naturally not accented, that is, in the 2/4 time to
the second beat, or to the second half of the first, by so-called
_syncopes_, the whole character of a piece is changed. In musical
passages in which many notes come upon one beat and the character
of which is light and pleasing, a peculiar charm is produced when
several rhythmical accents are made upon the same beat, and
likewise in slow passages the swelling of the tone upon the
accented note is very pleasing. Let the same phrase in a song
be sung with different rhythmical accents, and we may easily
see how such changes will give the passage quite another character.
The old Italian singers understood to a remarkable degree the
use of rhythm in the execution of vocal music. But the poetical
rhythm of the words accompanying the voice gives to the singer
a guide, reference to which shows him at least how and where
he may employ the nicer shades of musical rhythm.