COMPOSERS have a very prevalent habit of repeating themselves as much as possible. They write a theme, and alternate it with other music, but often insist on bringing back the original theme again, partly to give a finished and balanced effect to their work. They are very fond of doing this in the song-forms; the rondos are named from the procedure; and even in the freer sonata form the themes are followed by a development of their material, which in turn is succeeded by a repeat of the themes.
The shortest song-form in common use consists of two periods, each having a first phrase, known as the antecedent, and a second phrase, known as the consequent. In the two-period independent form, the phrases of the second period are made of wholly new material. In the two-period form with partial return, the consequent of the second period is derived from a phrase of the first, with no change or only slight alterations. The partial-return form is much more popular than the independent form, because of the tendency shown by composers to end as they began. Even when they use the two independent periods, they may suggest the original section by employing some of its material in a coda.
The best single volume for the study of the song-forms is the collection of Mendelssohn "Songs without Words." In these, an example of the two-part independent form is seen in no. 6, the first Venetian Gondola Song. As its title would imply, it is soothingly rhythmic, being in 6/8 time. An introduction defines the rhythm. The first period begins on the last beat of the seventh measure. Its antecedent is four measures long, while the consequent is prolonged to six measures, and ends on a cadence in the dominant key. A longer section of new material follows, having an antecedent of eight measures and a consequent of nine. The piece could end at that point; but the composer, following the prevalent impulse of letting some of the opening material return, added a coda based on the phrases of the first period.