Robin Williams and Paul Simon will join other stars on Monday for a show in New York in aid of the American Civil Liberties Union (ACLU).
Robin Williams will be among the performers
ACLU is protesting against a US Government demand that charities screen employees against being on a suspected terrorist "watch list".
Non-compliance would result in a charity losing support in raising funds from government employees.
Other stars taking part in the event include Richard Gere and Patti Smith.
Charities not complying with the demand would be excluded from the Combined Federal Campaign, which helps government and military staff donate to charities of their choice.
Composer Philip Glass, who is producing the ACLU event, said: "I need to live in an environment where there is a free exchange of ideas, not where the government is looking over my shoulder."
The show will also see a documentary tribute to the late comedian Lenny Bruce, who was well known for battling against censorship.
The US Government said the "watch list" was needed to deter potential terrorists.
British singer Yusuf Islam, formerly known as Cat Stevens, was last week revealed to be on the list when he was refused entry to the US.
Authorities said the refusal was on national security grounds.