Virtually every musical on Broadway shut down Friday as musicians went on strike, and actors and stagehands said they wouldn't cross their picket lines.

All weekend performances of 18 musicals, including such shows as 42nd Street, Hairspray, The Producers and The Phantom of the Opera, were canceled, too.

"They, unfortunately for theatergoers, have turned off the lights on Broadway," said Jed Bernstein, head of the League of American Theatres and Producers.

No more negotiations were scheduled for Friday and it was uncertain when they would resume.

"We remain ready and anxious to negotiate an agreement but when they close the theaters and provide us with what they are calling a final offer, it's very hard to negotiate," said union official Bill Dennison.

Shortly before the shutdown, the actors and stagehands expressed their solidarity with the musicians.

"Our members have made it clear: We do not want to perform to virtual orchestras," said Patrick Quinn, Actors' Equity president.

By the 8 p.m. curtain time, there were pickets in front of all the struck musicals. Outside the Ambassador Theatre, cast members of Chicago marched in support of the musicians.

"We want to maintain the integrity of performance on Broadway," said Belle Callaway, who currently plays Roxie Hart in the musical. "We want it to be worth the hundreds of dollars that people spend to come here -- the hotels, the food, everything."

Refunds or exchanges for all musicals were available.

Plays on Broadway -- such as Take Me Out and Frankie and Johnny in the Clair de Lune -- were being performed as usual, as were all off-Broadway productions. "Cabaret" was the only Broadway musical unaffected because it's covered by a special contract.

Broadway musicians last went on strike in September 1975, shutting down nine musicals for 25 days.

Earlier Friday, theater producers promised to keep their musicals running despite the musicians' walkout. The shows had intended to use either so-called virtual orchestras, computer-generated equipment, or tape as musical accompaniment, according to Bernstein.

But then the two other unions decided to support the musicians.

Stagehand union President Edward McConway said his rank and file were honoring the picket line "for the good of the industry and our membership."

"Even though we are concerned about the theatergoing public, the state of our industry and our city, we are a union and a union supports a union picket line. It's an issue of conscience," he said.

Pat Keifert, a tourist from St. Paul, Minn., who was in line at the Times Square booth where discount theater tickets can be purchased, said having a live orchestra was like "the difference between watching a baseball game and playing one. It's just a totally different dynamic. It's such an awesome difference."

But James Nicholas of Grand Rapids, Mich., said he was partial to producers. "The producers know what's economically doable and they make their adjustments," he said.

The main sticking point in negotiations with Local 802 of the American Federation of Musicians has been the question of minimums -- how many musicians are required for each show, a figure related to the size of each theater.

In negotiations last week, the producers proposed the number of musicians required for the large Broadway theaters be reduced to seven, a figure they later raised to 14. The minimums at those large theaters currently range from 24 to 26.

Producers originally wanted to do away with minimums altogether, saying they sometimes require shows to use more players than the shows need. The union says the minimums are essential to keep live music from disappearing on Broadway.

"We never had any intention of replacing live music with virtual orchestras and neither will we after this situation is resolved," Bernstein said.

Outside the Broadway Theatre, which houses "La Boheme," musicians picketed Friday.

Theater producers "are not going to reduce ticket prices. They're just going to get rid of musicians to add to their pockets. That's all this is about," said Marshall Coid, an onstage violinist for the musical "Chicago."

Live music on Broadway is important, Coid said. "Theater is live. It's reactive. It's in the moment. It changes, it's never the same."