on of "conclusion"
is easily overcome. In a word, there is no doubt of the unbroken
connection of these three phrases, despite the unusual weight of the
first cadence. See also the first cadence in Ex. 51.

By simply continuing the process of addition (and avoiding a decisive
perfect cadence) the phrase-group may be extended to more than three
phrases, though this is not common.

THE DOUBLE-PERIOD.--A third method consists in expanding the period
into a double-period (precisely as the phrase was lengthened into a
double-phrase, or period), _by avoiding a perfect cadence at the end of
the second phrase_, and adding another pair of phrases to balance the
first pair. It thus embraces four _coherent_ phrases, with a total
length of sixteen measures (when regular and unextended).

An important feature of the double-period is that the second period
usually resembles the first one very closely, at least in its first
members. That is, the second phrase contrasts with the first; _the
third corroborates the first_; and the fourth either resembles the
second, or contrasts with all three preceding phrases. This is not
always--though nearly always--the case.

The double-period in music finds its poetic analogy in almost any
stanza of four fairly long lines, that being a design in which we
expect unity of meaning throughout, the progressive evolution of one
continuous thought, uniformity of metric structure (mostly in
_alternate_ lines), the corroboration of rhyme, and, at the same time,
some degree and kind of contrast,--as in the following stanza of
Tennyson's:

Phrase 1. "The splendor falls on castle walls,
Phrase 2. And snowy summits old in story;
Phrase 3. The long light shakes across the lakes,
Phrase 4. And the wild cataract leaps in glory."

The analogy is not complete; one is not likely to find, anywhere,
absolute parallelism between music and poetry; but it is near enough to
elucidate the musical purpose and character of the double-period. And
it accounts for the very general choice of this form for the hymn-tune.

The following illustrates the double-period, in its most regular and
convincing form (Beethoven, pianoforte sonata, op. 49, No. 1):--

[Illustration: Example 51. Fragment of Beethoven.]

Each phrase is four measures long, as usual; the first one ends (as in
Ex. 50) with one of those early, transient perfect cadences that do not
break the continuity of the sentence; the secon