In western music, the classical period means music from about 1750 to 1825. It was the time of composers like Joseph Haydn, Wolfgang Amadeus Mozart and Ludwig van Beethoven. Orchestras became bigger, and composers often wrote longer pieces of music called symphonies that had several sections (called movements). Some movements of a symphony were loud and fast; other movements were quiet and sad. The form of a piece of music was very important at this time. Music had to have a nice 'shape'. They often used a structure which was called sonata form.