From today's Globe (http://www.boston.com/news/local/massachusetts/articles/2003/11/17/subway_musicians_unplugged/):
...MBTA officials have deemed nonacoustic music a hazard in T stations. Beginning Dec. 1, they are banning electric keyboards and guitars, microphones, and amplifiers, saying they drown out important messages on the public address system. Saxophones, trumpets, and horns of any kind also will be forbidden.
Performers are calling the new rules 'discriminatory," "arrogant," and "unconstitutional." The Subway Artists Guild filed a complaint with the American Civil Liberties Union on Friday. Guild members were looking for a lawyer over the weekend to represent them in a legal challenge of the policy, which they say threatens to put many performers out of business.
"It's devastating," said Stephen Baird, head of the guild. "It's drastic overkill."