Ternary form
Ternary form, sometimes called song form,[1] is a three-part musical form consisting of an opening section (A), a following section (B) and then a repetition of the first section (A). It is usually schematized as A–B–A. Prominent examples include the da capo aria "The trumpet shall sound" from Handel's Messiah, Chopin's Prelude in D-Flat Major "Raindrop", (Op. 28)[2] and the opening chorus of Bach's St John Passion.
"Song form" redirects here. For the verse-chorus structure found in various songs, such as pop songs, see Song structure.Ternary form within a ternary form[edit]
In a complex ternary form each section is itself in ternary form in the scheme of [(A–B–A)(C–D–C)(A–B–A)] By convention each part is repeated and only on its first rendition: [(A–A–B–B–A)(C–C–D–D–C)(A–B–A)] .[8] An example are the Impromptus (Op. 7) by Jan Voříšek.[9]
Expanded ternary forms are especially common among Romantic-era composers; for example, Chopin's "Military" Polonaise (Op. 40, No. 1) is in the form [(A–A–B–A-B–A)(C–C–D–C-D–C)(A–B–A)], where the A and B sections and C and D sections are repeated as a group, and the original theme returning at the end without repeats.