The 32-bar form, also known as the AABA song form, American popular song form and the ballad form, is a song structure commonly found in Tin Pan Alley songs and other American popular music, especially in the first half of the 20th century.
The song form consists of four sections: an eight-bar A section; a second eight-bar A section (which may have slight changes from the first A section); an eight-bar B section, often with contrasting harmony or "feel"; and a final eight-bar A section. The core melody line is generally retained in each A section, although variations may be added, particularly for the last A section.