What was the international language of music during Classical period?

The international language of music during the Classical period was Italian. This was due in part to the fact that Italy was the birthplace of opera, and Italian opera was the most popular form of musical entertainment in Europe during the 18th century. As a result, Italian musical terms and expressions became widely adopted by musicians all over the world. Even today, many musical terms are still used in their original Italian form, such as allegro, andante, and forte.