n Folk-music. This principle[32]
of "Thematic Development"--the chief idiom of instrumental music--by
which a motive or a theme is expanded into a large symphonic movement,
was worked out in that type of music known as the Polyphonic or
many-voiced; and Polyphonic music became, in turn, the point of
departure for our modern system of harmony, with its methods of key
relationship and of modulation. As we have stated in Chapter I, the
principle of systematic repetition or imitation--first discovered and
partially applied by the musicians[33] of the early French School and
by the Netherland masters--finally culminated in the celebrated vocal
works (a capella or unaccompanied) composed by Palestrina and his
contemporaries for the Roman Catholic Liturgy. Up to this point the
whole texture of music had been conceived in connection with voices;
but with the development of the organ, so admirably suited for
polyphonic style, and the perfection of the family of stringed
instruments, the principles of polyphony were carried over and applied
to instrumental treatment. The composer who, through his constructive
genius, most fully embodied these principles[34] was John Sebastian
Bach (1685-1750). We are now prepared to explain the characteristics
of polyphonic music and then to analyze some typical examples from
Bach and other polyphonic composers. The essential difference between
homophonic and polyphonic style is implied by the terms themselves.
When there is but one melody, the skill of the composer and the
attention of the listener are concentrated upon this single melodic
line; and even if there be an accompaniment, it is so planned that the
chief melody stands out in relief against it. The pre-eminence of this
chief melody is seldom usurped, although the accompaniment often has
interesting features of its own. As soon as we have more than one
melody (whether there be two, three or still others) all these
voice-parts may be of coequal importance, and the musical fabric
becomes an interwoven texture of a number of strands. The genius and
skill of the composer is now expended on securing life and interest
for each of these voices--soprano, alto, tenor, bass--which seem to be
braided together; and thus a much more comprehensive attention is
required of the listener. For instead of the single melody in the
soprano, or upper voice, of the Folk-song, we now must listen
consciously to the bass and to both of the inner voices.[35] Too m