St. Louis ? When the St. Louis Symphony Orchestra crashed to the brink of bankruptcy four years ago, local residents opened their wallets wide to keep the music playing.

Thousands of patrons gave to rescue the nation’s second-oldest orchestra — one that brought world-class talent to Powell Symphony Hall. In three and a half years, the community raised $130 million.

Last week, they found out it wasn’t enough.

Instead of rehearsing with their new music director, acclaimed conductor David Robertson, the symphony’s 93 musicians were walking a picket line. This weekend’s concerts were canceled. And the rest of the season is in jeopardy.

The musicians are demanding that the symphony dip into its donation-fattened endowment to give them raises. Management refuses, insisting that the fund be left intact to ensure the 125-year-old symphony never again faces bankruptcy.

The impasse here is a reflection of the strains threatening orchestras across the nation.

Intense and often divisive contract negotiations consumed three of the nation’s top orchestras last fall: Chicago, Cleveland and Philadelphia. All were settled without strikes. But analysts say they and many smaller groups are struggling to produce music amid a financial crunch brought on by the high cost of health benefits, a decrease in ticket sales and the challenge of attracting donations in a still-struggling economy.

Close to 90 percent of the country’s orchestras ran a budget deficit last year, according to Jack McAuliffe, vice president of the American Symphony Orchestra League, a trade association. “The last three or four years have been very challenging,” he said.

To survive, both musicians and management have had to give.

An employee of Powell symphony Hall, home of the St. Louis Symphony Orchestra, mops the stage. The hall may remain empty during the winter concert season if musicians and management do not reach an agreement on a pay increase.

Contracts that traditionally set rigid limits on rehearsal times and performance dates have been amended so orchestras can attract new audiences.

In Philadelphia, musicians have agreed for the first time to perform on Sundays. St. Louis offers Friday morning concerts, over doughnuts, to attract senior citizens reluctant to drive at night. The New York Philharmonic stages occasional concerts from 5 p.m. to 6 p.m.; they’re billed as a chance for commuters to avoid the evening rush hour by staying in the city with Brahms or Beethoven instead.

In a bid for a younger audience, the artistic director of the Chicago Symphony teams up with a local rock-station DJ for pre-concert discussions several times a season. The Los Angeles Philharmonic has pioneered flexible contracts that allow for the orchestra to be broken up into smaller ensembles and chamber groups from time to time.

And in this year’s contract negotiations, musicians in both Chicago and Philadelphia agreed to cut a few full-time positions — a painful concession in the classical music world, where hundreds of musicians might audition for a single open seat.

“There’s a lot of stress among high-level management at every symphony I’ve talked to,” said Arthur Brooks, director of the nonprofit studies program at the Maxwell School of Public Affairs at Syracuse University. “They’re really having to think outside the box.”