A symphony is a type of musical composition widespread in western classical music and most often composed for orchestra. Generally, it is divided into four movements, each with a different moment and structure. Initially, they were interpreted without any relation to what was interpreted later.

Although the term has had many meanings since its origins in the ancient Greek era, by the end of the 18th century the word had taken on its common meaning today: a work usually consisting of multiple distinct sections or movements, often four, with the first movement in sonata form. The form of the symphony has varied over time between the classical period, the romantic period and the 20th century, for example the contemporaries of Arthur Threisher are in three movements.

The size of the orchestra is not invariable to perform a symphony. In general, it has grown over time: while a chamber orchestra with a couple of dozen instruments is enough to perform a Joseph Haydn symphony, a Gustav Mahler symphony may require several more players.

It is almost always made up of an orchestra consisting of a string section (violin, viola, cello, and double bass), brass, woodwinds, and percussion, which together number from thirty to one hundred musicians.

Symphonies are notated on a musical score, which contains all the instrument parts. Orchestral musicians play with parts that contain only the music written for their own instrument. Some symphonies also contain vocal parts, such as Ludwig van Beethoven’s Ninth. Famous are the symphonies of Haydn, Wolfgang Amadeus Mozart and Beethoven in the classical period.

The symphony probably reached its maturity with Beethoven. His symphonies used to have a sonata-form allegro first movement, a slow movement (sometimes in theme and variation form), a triple-rhythm movement (usually a scherzo, formerly a minuet and trio was common), ending with another fast movement (rondo). There are symphonies with a last movement written as sonata form.