17 U.S.C. 110(7)
Limitations on exclusive rights: Exemption of certain performances and displays

Notwithstanding the provisions of section 106, the following are not infringements of copyright: ... (7) performance of a nondramatic musical work by a vending establishment open to the public at large without any direct or indirect admission charge, where the sole purpose of the performance is to promote the retail sale of copies or phonorecords of the work, or of the audiovisual or other devices utilized in such performance, and the performance is not transmitted beyond the place where the establishment is located and is within the immediate area where the sale is occurring; ...