Performance is the physical expression of music. Often, a musical work is performed once its structure and instrumentation are satisfactory to its creators; however, as it gets performed, it can evolve and change. A performance can either be rehearsed or improvised. Improvisation is a musical idea created without premeditation, while rehearsal is vigorous repetition of an idea until it has achieved cohesion. Musicians will sometimes add improvisation to a well-rehearsed idea to create a unique performance.

Many cultures include strong traditions of solo and performance, such as in Indian classical music, and in the Western Art music tradition. Other cultures, such as in Bali, include strong traditions of group performance. All cultures include a mixture of both, and performance may range from improvised solo playing for one's enjoyment to highly planned and organised performance rituals such as the modern classical concert, religious processions, music festivals or music competitions. Chamber music, which is music for a small ensemble with only a few of each type of instrument, is often seen as more intimate than symphonic works.

Many types of music, such as traditional blues and folk music were originally preserved in the memory of performers, and the songs were handed down orally, or aurally (by ear). When the composer of music is no longer known, this music is often classified as "traditional". Different musical traditions have different attitudes towards how and where to make changes to the original source material, from quite strict, to those which demand improvisation or modification to the music. A culture's history may also be passed by ear through song.

The detail included explicitly in the music notation varies between genres and historical periods. In general, art music notation from the 17th through the 19th century required performers to have a great deal of contextual knowledge about performing styles. For example, in the 17th and 18th century, music notated for solo performers typically indicated a simple, unornamented melody. However, it was expected that performers would know how to add stylistically-appropriate ornaments such as trills and turns. In the 19th century, art music for solo performers may give a general instruction such as to perform the music expressively, without describing in detail how the performer should do this. It was expected that the performer would know how to use tempo changes, accentuation, and pauses (among other devices) to obtain this "expressive" performance style. In the 20th century, art music notation often became more explicit and used a range of markings and annotations to indicate to performers how they should play or sing the piece.