Joseph Haydn was one of the most prolific and prominent composers of the classical period. He is often called the "Father of the Symphony" and "Father of the String Quartet" because of his important contributions to these genres. He was also instrumental in the development of the piano trio and in the evolution of sonata form. A life-long resident of Austria, Haydn spent much of his career as a court musician for the wealthy Hungarian aristocratic Esterhazy family on their remote estate. Isolated from other composers and trends in music until the later part of his long life, he was, as he put it, "forced to become original". At the time of his death, he was one of the most celebrated composers in Europe. Joseph Haydn was the brother of Michael Haydn, himself a highly regarded composer, and Johann Evangelist Haydn, a tenor. He was also a close friend of Wolfgang Amadeus Mozart and a teacher of Ludwig van Beethoven.