History: The New York City Subway, United States

At present, more than 100 soloists and groups participate in MUNY providing over 150 weekly performances at 25 locations throughout the transit system. For example, Mr. M. Salieu Suso, a kora player from The Gambia, plays at Union Square.
In addition, any musician/entertainer may perform in subway mezzanines and platforms. On platforms, there may be no amplifications as this is part of MTA policies:
“The New York City Transit (NYCT) is a subdivision of the Metropolitan Transportation Authority (MTA) that operates the city's subways and buses. The NYCT authorizes these types of free expression in subway stations: "Public speaking; distribution of written materials; solicitation for charitable, religious or political causes; and artist performances, including the acceptance of donations.”
Performers must not be within 25 feet (7.6 m) of a token booth or 50 feet (15 m) from a MTA office/tower, blocking access to an escalator, stairwell, or elevator, interfering with transit services or passenger movement; or in an area where construction is occurring. In addition, performance is prohibited during public service announcements and may be no louder than 85 dBA at 5 feet (1.5 m) away or 70 dBa at 2 feet (0.61 m) from a token booth. Performances are prohibited in subway cars.