ing to _fall_, the reference being to the falling of the
voice (_i.e._, the dropping to the normal pitch) at the close
of a sentence.

203. The most frequent cadence in harmony is that involving the chord on
I preceded by the chord on V. Because of its directness the cadence V--I
is called the _authentic cadence_.

204. The most satisfactory form (to the ear) of the authentic cadence is
that in which the highest voice (the soprano) of the final chord is the
_root_ of that chord. When the final chord appears in this position the
cadence is called _perfect_[36] _authentic_, and when the third or
fifth of the chord appear in the soprano, the cadence is called
_imperfect authentic_. Fig. 68 shows the chord G--B--D cadencing to
C--E--G in three different ways. The first one (a) is called a _perfect
authentic cadence_, but the last two (c) and (d) are _imperfect
authentic_.

[Footnote 36: Many theorists (including Durand in his monumental
"Treatise on Harmony") consider the V--I cadence to be the only one
which may legitimately be called _perfect_, but the majority of writers
seem to take the view that either authentic or plagal cadence may be
either perfect or imperfect, depending upon the soprano tone, as noted
above.]

[Illustration: Fig. 68.]

205. A _plagal cadence_ is one in which the tonic chord is preceded by
the sub-dominant chord (IV--I). The _plagal cadence_ (sometimes called
the _church cadence_, or _amen cadence_), like the authentic, is
described as being _perfect_ when the soprano of the tonic chord is the
root of that chord, and _imperfect_ when the soprano of the final chord
is the third or fifth of that chord. Fig. 69 shows the chord F--A--C
cadencing to C--E--G in three ways. The first one (a) is called a
_perfect plagal cadence_, the last two are _imperfect plagal_.

[Illustration: Fig. 69.]

206. A _half-cadence_ occurs when the dominant chord is used as the
final chord of a phrase, and is immediately preceded by the tonic chord.
This form is used to give variety in the course of a composition, but is
not available at the end because it does not give a definite close in
the tonic key. Fig. 70 shows the use of the _half-cadence_ at the close
of such a phrase.

[Illustration: Fig. 70. BACH]

207. A _deceptive cadence_ is the progression of the dominant chord to
some other chord than the tonic, the word _deceptive_ implying that the
ear expects to hear V resolve to I and is deceived whe