Complex sentence: Clément sang at the Metropolitan Opera in New York from 1909 to 1911, and in Boston, from 1911 to 1913, where he was much admired for his stylish singing and elegance on stage, considered one of the greatest Roméo and Don José of his time.
Split into simpler sentences: Clément sang at the Metropolitan Opera in New York from 1909 to 1911, and in Boston, from 1911 to 1913. He was much admired for his stylish singing and elegance on stage, considered one of the greatest Roméo of his time.