What is the most common form of western music AB ABBA ABC or ABA?

The most common form of western music is ABA. This is a ternary form, meaning it consists of three sections. The first section (A) is the main theme, the second section (B) is the contrasting section, and the third section (A) is a repeat of the main theme. This form is often used in popular music, folk music, and classical music.