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.

For example, in the 17th and 18th century, refrain notated for solo performers practically indicated a simple, unornamented melody. However, it was expected that Personalized Music performers would know how to add fuel stylistically-appropriate ornaments such as trills and turns. In the 19th century, art measure for solo performers may give a general instruction such as to perform the bebop expressively, without describing in detail how the performer should do this.