ically
interesting, and the "harmony" is the result of combining several
melodies in such a way as to give a pleasing effect, instead of treating
a melody by adding chords as an accompaniment or support. Counterpoint,
canon, round, fugue, etc., are all _polyphonic_ in style. The word
_contrapuntal_ is often used synonymously with _polyphonic_.

(Sections 139 to 143 relate especially to terms describing
polyphonic music.)

139. _Counterpoint_ is the art of adding one or more parts or melodies
to a given melody, the latter being known as the "cantus firmus," or
subject. It may therefore be broadly defined as "the art of combining
melodies."

The word _counterpoint_ comes from the three words "_punctus
contra punctum_," meaning "point against point." The word
point as here used refers to the _punctus_--one of the neumae
of the mediaeval system, these neumae being the immediate
predecessors of modern notes.

Both vocal and instrumental music have been written in
contrapuntal style. The familiar two- and three-part
"inventions" by Bach are excellent examples of instrumental
counterpoint, while such choruses as those in "The Messiah" by
Handel illustrate the highest type of vocal counterpoint.

140. _Imitation_ is the repetition by one part, of a subject or theme
previously introduced by another part. If the imitation is exact, the
term _strict imitation_ is applied, but if only approximate, then the
term _free imitation_ is used in referring to it. The repetition need
not have the exact pitches of the subject in order to be _strict_; on
the contrary the imitation is usually at the interval of an octave, or a
fifth, or a second, etc. Fig. 57 shows an example of strict imitation in
which the _third_ part comes in an octave _lower_ than the first part.

141. A _canon_ is a contrapuntal composition in the style of strict
imitation, one part repeating exactly (but at any interval) what another
part has played or sung. The term "canonic style" is sometimes applied
to music in which the imitation is not exact. An example of three-part
canon is given in Fig. 57.

[Illustration: CANON IN THREE VOICES, IN THE UNISON AND OCTAVE

Fig. 57. MOZART]

The word _canon_ means _law_, and was applied to this
particular form of composition because the rules relating to
its composition were invariable. It is because of this
non-flexibility that the _canon_