phrases, and periods._]

It will be as apparent to the eye of one who cannot read music as it
will to his ear when he hears this melody played, that it is built up
of two groups of notes only. These groups are marked off by the heavy
lines across the staff called bars, whose purpose it is to indicate
rhythmical subdivisions in music. The second, third, fifth, sixth, and
seventh of these groups are repetitions merely of the first group,
which is the germ of the melody, but on different degrees of the
scale; the fourth and eighth groups are identical and are an appendage
hitched to the first group for the purpose of bringing it to a close,
supplying a resting-point craved by man's innate sense of symmetry.
Musicians call such groups cadences. A musical analyst would call each
group a motive, and say that each successive two groups, beginning
with the first, constitute a phrase, each two phrases a period, and
the two periods a melody. We have therefore in this innocent Creole
tune eight motives, four phrases, and two periods; yet its material is
summed up in two groups, one of seven notes, one of five, which only
need to be identified and remembered to enable a listener to recognize
something of the design of a composer if he were to put the melody to
the highest purposes that melody can be put in the art of musical
composition.

[Sidenote: _Repetition in music._]

Repetition is the constructive principle which was employed by the
folk-musician in creating this melody; and repetition is the
fundamental principle in all musical construction. It will suffice for
many merely to be reminded of this to appreciate the fact that while
the exercise of memory is a most necessary activity in listening to
music, it lies in music to make that exercise easy. There is
repetition of motives, phrases, and periods in melody; repetition of
melodies in parts; and repetition of parts in the wholes of the larger
forms.

[Sidenote: _Repetition in poetry._]

The beginnings of poetic forms are also found in repetition; in
primitive poetry it is exemplified in the refrain or burden, in the
highly developed poetry of the Hebrews in parallelism. The Psalmist
wrote:

"O Lord, rebuke me not in thy wrath,
Neither chasten me in thy hot displeasure."

[Sidenote: _Key relationship._]

Here is a period of two members, the latter repeating the thought of
the former. A musical analyst might find in it an admirable analogue
for the first p