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 second phrase ends with a semicadence,--therefore the sentence remains unbroken; phrase three is _exactly_ like the first, and is therefore an Antecedent, as before; phrase four bears close resemblance to the second one, but differs at the end, on account of the perfect cadence.