Library (music) is the name given to recorded music produced and owned by production music libraries and licensed to customers for use in film, television, radio and other media.
Unlike popular and classical music publishers, who typically own less than 50 percent of the copyright in a composition, production music libraries own all of the copyrights of their music. Thus, it can be licensed without the composer's permission, as is necessary in licensing music from normal publishers. This is because virtually all music created for music libraries is done on a work for hire basis. Production music is a convenient solution for media producers—they can be assured that they will be able to license any piece of music in the library at a reasonable rate, whereas a specially-commissioned work could be prohibitively expensive. Similarly, licensing a well-known piece of popular music could cost anywhere from tens to hundreds of thousands of dollars, depending on the prominence of the performer(s).