This article was updated at 9:18 p.m.

NEW YORK — Broadway staged a quick comeback Tuesday.

Mayor Michael Bloomberg called in a mediator Monday night to settle the four-day musicians’ strike that shuttered 18 Broadway musicals over the weekend. Heralding a new four-year contract between the musicians and the producers, Bloomberg announced Tuesday morning that all shows affected by the strike would resume performances that evening.

“Broadway is no longer dark. It is a happy ending,” Bloomberg said, flanked by more than 30 Broadway powerbrokers at a hastily arranged Gracie Mansion press conference Tuesday morning.

In 1975, Mayor Abe Beame waited 24 days to bring in a mediator to settle a musicians’ strike. This time around, Gotham’s top man waited just four days before he got involved.

“Timing is everything,” Bloomberg said. “Both sides needed the time to go back to their members to talk over the weekend and assess the situation. If (the mediation) had happened any earlier, it wouldn’t have worked.”

Mediator brought in

On Monday, Bloomberg appointed Frank J. Macchiarola, the former chancellor of the New York City public schools, to be the mediator in contract negotiations between the League of American Theaters & Producers and Local 802 of the American Federation of Musicians. There had been no talks between the two sides since Friday night, shortly after the musicians went on strike. Stagehands and actors subsequently honored their picket lines.

“I’m not sure how I got involved,” said Macchiarola, the current president of St. Francis College in Brooklyn. The mediator said he began talks at Gracie Mansion Monday night with a prayer by St. Francis: “It is in giving that we receive.”

Which side received more will be debated for months to come.

The new four-year contract keeps the controversial union-mandated requirement of musician minimums, but drops the number from 26 and 24 to 19 and 18 musicians at Broadway’s 13 largest theaters.

The league had sought to entirely eliminate the practice its leaders called “antiquated” and “featherbedding.”

Edging together

In negotiations last week, the union dropped its top number to 24. The league made counter-offers of seven and then 15. Neither side made compromises over the weekend on the issue.

At the Gracie Mansion press conference, Local 802 president William Moriarity announced the new minimum numbers but emphasized an important caveat.

“While it is a four-year contract, the new minimums will remain in place for 10 years,” he said. Putting an upbeat spin on the outcome, the union prexy added, “We preserve live music. We have the largest staff minimums in the world.”

League president Jed Bernstein said minimums established under the old contract remain in place for musicals already up and running.

“Neither side got everything it wanted,” Bernstein said. “There were significant compromises on both sides. We are happy our musician family is back with us.”

He also thanked Macchiarola. “Frank is a quick study,” he said.

Some winners

Over the past two weeks, both Moriarity and Bernstein had expressed satisfaction with negotiations regarding the issue of special situations. In 1993, the two sides established an arbitration committee to which producers could appeal to lower the minimums. In the last decade, 19 musicals sought petitions to the committee. Four withdrew and seven, including “Mamma Mia!” and “Urban Cowboy,” were granted lower minimums than their respective theaters required.

During the current contract negotiations, general manager Alan Wasser (“The Phantom of the Opera”) disparaged the special situations. “It doesn’t work,” he said at a league press conference. “Four members of the arbitration committee are union members, only two are not. They are under pressure to side with the union.”

Producers may be happier with the special situations clause in the new contract.

No strings

“We have changed the makeup of the committee and the criteria of musicals,” Moriarity said. “The six names on the committee are neutrals; all of them are neither members of the union or the league.”

The musicians get a 2.75% raise each year of the new contract.

Bernstein said he did not know how the strike would affect the opening nights of incoming musicals.

“It depends on how fast they can get up,” he said.

A spokesman for “Urban Cowboy” said the tuner would open March 27, as originally scheduled. It was expected to perform Tuesday night, but has canceled today’s matinee. Reps for other incoming musicals — “Frog and Toad,” “Gypsy,” “The Look of Love” and “Nine” — expected their tuners to remain on sked.

Tuesday’s press conference at Gracie Mansion brought out Broadway’s big guns. In addition to Moriarity, Bernstein and Macchiarola, the mayor was joined at the podium by the Shubert’s Gerald Schoenfeld and Phil Smith, the Nederlanders’ Nick Scandalios, Jujamcyn’s Paul Libin, Local 802’s Bill Dennison, Cameron Mackintosh’s Alan Wasser and the producers Barry Weissler and Kevin McCollum, among others.

Saturday’s big vote

However, it’s not over until the horn player toots.

Although the union and the league came to an agreement, the new contract must be ratified by the rank-and-file of Local 802. That vote is expected to take place Saturday.

“This could be an initial wave of anger, but several musicians think we lost,” said one union member. She worried that Local 802 would lose the support of the stagehands and actors if the new contract weren’t ratified. “I think this is the best deal we could get, but many others in the pit disagree.”

One producer pointed out that, according to the new minimums, Local 802 lost approximately 65 jobs. One union exec countered the new agreement protected about 300 jobs for 10 years “in the face of new technology.”

Who are the neutrals on the new “special situations” arbitration committee? A few names have been circulated by sources close to negotiations. They include Ted Chapin, president of the Rodgers & Hammerstein Organization; Victoria Traube, special VP at R&H; Freddie Gershon, owner of Music Theater Intl.; and Sargent Aborn, president of Tams Witmark Music Library.