The name of which musical composition in Greek means "agreement or concord of sound"?

A "symphony" is an extended musical composition in Western classical music, most often for orchestra. Although the term has had many meanings from its origins in the ancient Greek era, by the late 18th century the word had taken on the meaning common today: a work usually consisting of multiple distinct sections or movements, often four, with the first movement in sonata form.

Symphonies are almost always scored for an orchestra consisting of a string section (violin, viola, cello, and double bass), brass, woodwind, and percussion instruments which altogether number about 30 to 100 musicians.

The word "symphony" is derived from the Greek word συμφωνία (symphonia), meaning "agreement or concord of sound", "concert of vocal or instrumental music", from σύμφωνος (symphōnos), "harmonious".

In late Greek and medieval theory, the word was used for consonance, as opposed to διαφωνία (diaphōnia), which was the word for "dissonance".

In the sense of "sounding together," the word begins to appear in the titles of some works by 16th- and 17th-century composers.