what is a rondo

A rondo is a musical form that alternates a principal theme with one or more contrasting themes, called episodes. The form is represented by letters that correspond to certain portions of music, with the most common being ABACA and ABACABA. The A section is the main theme, also known as the refrain, which returns throughout the work, while the B, C, and other sections are contrasting themes or episodes. The form can include a variety of tempos and styles, but the character of a rondo is typically fast and vivacious. The rondo was a popular musical structure during the Classical and Romantic eras and was frequently used in sonatas, symphonies, chamber works, concerti, and operas.