In which formal musical structure is section A heard three times or more in the tonic key?

Rondo form is characterized by the recurring theme, referred to as section A, which is presented multiple times in the tonic key. This structure typically involves a pattern where the main theme alternates with contrasting sections. The repetition of section A creates a sense of unity and familiarity throughout the piece, while the contrasting sections provide variety and interest.

In Rondo form, the sequence might look like A-B-A-C-A-D-A, where the A theme comes back several times, highlighting the tonal center. This feature makes Rondo a popular choice for composers seeking to create a lively and engaging musical experience.

In contrast, other forms such as Sonata form, while also integral to classical music, follow a different structure focusing primarily on exposition, development, and recapitulation of themes rather than the frequent reiteration of a specific section in the tonic key. Cyclic form involves a recurring theme across movements, often seen in larger works, and theme and variations present a theme followed by a series of variations rather than repetitive returns to the original theme in its unaltered state.