An orchestra is a large instrumental ensemble that typically includes strings, woodwinds, brass, and percussion. The modern symphony orchestra may number from about sixty to more than a hundred players and is usually led by a conductor.

The string section forms the core, with multiple players on each part. Woodwinds and brass provide color, power, and solo lines. Percussion adds rhythm and dramatic accents. The exact instrumentation varies according to the repertoire, from the smaller Classical orchestra to the expanded forces of late Romantic and modern works.

Orchestras perform symphonies, concertos, opera and ballet scores, and a wide range of other music. Rehearsals under the conductor refine balance, intonation, and interpretation. The collective sound of a fine orchestra is one of the great achievements of musical collaboration.

• Large ensemble of strings, winds, brass, percussion
• Usually led by a conductor
• Performs symphonic and related repertoire
• Varies in size according to the music