During the Classical period, symphonies, concertos and sonatas were all based
on a compositional formula known as sonata form. Composers used sonata
form as a means of providing structure to their compositions. It
became the most popular compositional form to be used throughout the Classical
The word "sonata" was first
used as the title of any piece to be "sounded" (played on a musical instrument).
A short sonata was called a sonatina. By the late 1700s, the sonata
had become a more formal composition, usually containing three or four
contrasting movements, of which the form of the first movement was the
The first movement of a sonata
is in strictly "sonata form." This means that it consists of three
sections. In the first section, the exposition, the melodies
are "exposed" or introduced. Secondary themes are often in a key
a fifth higher than the tonic (original key). The second section
is called the development and in this section themes are altered
and used however the composer wishes. The third section, named the
restates all the themes, but this time all are in the tonic key.
Sometimes sonata form includes an introduction and a coda.
Piano Sonata No. 21 in C "Waldstein" (Op. 53) by Ludwig van Beethoven