Final answer:
The Sonata and Rondo are the musical forms that were perfected during the Classical Era, primarily by composers like Haydn, Mozart, and Beethoven.
Step-by-step explanation:
The musical forms that were perfected during the Classical Era are the Sonata and Rondo. The Classical Era was marked by an emphasis on clarity, balance, and form, which these musical structures exemplify. Composers such as Haydn, Mozart, and Beethoven developed these forms to a high degree, and their works are paradigms of the Classical style. The Sonata form became particularly important for its use in symphonies, chamber music, and sonatas, characterized by its three main sections: exposition, development, and recapitulation. The Rondo form, known for its recurring main theme alternating with contrasting sections, also became highly popular during this period. On the other hand, forms like Fugue and Opera originated before the Classical Era but were still prominent. However, the Gregorian Chant, Madrigal, Barcarolle, and Ballade were not musical forms perfected during the Classical Era.