Long musical composition for orchestra, usually in several movements. The term (meaning sounding together) came to be the standard name for instrumental episodes, and especially overtures, in early Italian opera. The late-17th-century Neapolitan opera overture, or sinfonia, as established especially by Alessandro Scarlatti c. 1780, had three movements, their tempos being fast-slow-fast. Soon such overtures began to be performed by themselves in concert settings, like another forerunner of the symphony, the concerto grosso. The two merged in the early 18th century in the symphonies of Giovanni Battista Sammartini (1700/01–75). In c. 1750 German and Viennese composers began to add a minuet movement. Joseph Haydn, the father of the symphony, wrote more than 100 symphonies of remarkable originality, intensity, and brilliance in the years 1755–95; since Haydn, the symphony has been regarded as the most important orchestral genre. Wolfgang Amadeus Mozart wrote about 35 original symphonies. Ludwig van Beethoven's nine symphonies endowed the genre with enormous weight and ambition. Later symphonists include Franz Schubert, Felix Mendelssohn, Robert Schumann, Anton Bruckner, Johannes Brahms, Antonín Dvorák, Pyotr Ilyich Tchaikovsky, and Gustav Mahler; their 20th-century successors include Ralph Vaughan Williams, Jean Sibelius, Dmitry Shostakovich, and Witold Lutoslawski.