ith some
other part of the chord than the keynote as uppermost (or lowermost)
tone_. This might appear to lighten the perfect cadence too
immaterially to exercise so radical an influence upon the value
(weight) of the interruption. The _keynote_, however, is so decisive
and final in its harmonic and melodic effect--everywhere in music--that
its absence more or less completely cancels the terminating quality of
the cadence-chord; in other words, the force of a tonic cadence depends
upon the weight and prominence of the _keynote_.

For example:

[Illustration: Example 36. Fragment of Schubert.]

The first, second, and third of these cadences is made upon the tonic
harmony, on the accent of each successive fourth measure. But they are
only _semicadences_, as the melody (uppermost part) rests upon the
Third of the chord, _c_, instead of the keynote; this substitution of
_c_ for _a-flat_ is sufficient to frustrate the perfect cadence and
diminish it to a transient interruption. The final cadence is perfect,
however, because there the uppermost tone _is_ the keynote. See also
Ex. 21; and Ex. 17, No. 2, fourth measure (semicadence, with _a_
instead of _f_ as principal tone in upper part, and disguised by the
continuation of rhythmic movement to the end of the cadence-measure).
In Ex. 17, No. 1, the cadence is made with the tonic harmony of G
minor, but with the Third (_b-flat_) at the top.

LOCATING THE CADENCES.--Next to the recognition and comparison of the
different melodic sections of a composition (in a word, the _melodic
delineation_ of the whole), the most significant task in music analysis
is the locating and classifying of the cadences. They are the angles
of the design, so to speak; and have the same bearing upon the sense of
the music as punctuation marks have in rhetoric. Intelligent and
effective phrasing, adequate interpretation of the composer's purpose,
is impossible without a distinct exposition of the cadences,--if not of
the inferior points of interruption between motives, also.

The best general rule for locating cadences is, probably, to look for
them in the right place, namely, in the _fourth measure_ from the
beginning of each phrase. The fairly regular operation of this rule
has been verified in Lesson 4. But exceptions have also been seen (in
Ex. 17), and many more are certain to be encountered, simply because
the principle of Unity (exemplified by the prevalence of the
four-measure