In the visual arts, it is not uncommon in either fine art or commercial art such as comics for a number of assistants to do work on a piece that is credited to a single artist Andy Warhol engaged in this practice, supervising an assembly line silk screen process for his artwork. In hip hop music, the increasing use of ghostwriters by high-profile hip-hop stars has led to controversy. A pop music ghostwriter writes lyrics and a melody in the style of the credited musician. Composers have long hired ghostwriters to help them to write musical pieces and songs Wolfgang Amadeus Mozart is an example of a well-known composer who was paid to ghostwrite music for wealthy patrons. Ghostwriting (or simply "ghosting") also occurs in other creative fields. Sometimes the ghostwriter is acknowledged by the author or publisher for his or her writing services, euphemistically called a "researcher" or "research assistant", but often the ghostwriter is not credited. Usually, there is a confidentiality clause in the contract between the ghostwriter and the credited author that obligates the former to remain anonymous. Screenplay authors can also use ghostwriters to either edit or rewrite their scripts to improve them. In music, ghostwriters are often used to write songs, lyrics, and instrumental pieces. Memoir ghostwriters often pride themselves in "disappearing" when impersonating others since such disappearance signals the quality of their craftsmanship. Celebrities, executives, participants in timely news stories, and political leaders often hire ghostwriters to draft or edit autobiographies, memoirs, magazine articles, or other written material. As a result, his publisher hired ghostwriters to write novels in the Clancy style.Ī ghostwriter is hired to write literary or journalistic works, speeches, or other texts that are officially credited to another person as the author. The popular demand for Tom Clancy's action novels exceeded his ability to write new books.