When Baltimore Symphony Orchestra players laid down their instruments in favor of picket signs a month ago, they were following a long tradition of militancy among symphony orchestra musicians. In the past 10 years, the 31 major orchestras in the United States have struck or been locked out 28 times, according to the American Symphony Orchestra League. ``Musicians in general traditionally have been the most militant of the various entertainment groups,'' said Leonard Leibowitz, an attorney who represents Baltimore Symphony members and the American Federation of Musicians. ``Symphony musicians in particular have probably been one of the most militant.'' The Baltimore orchestra has gone on strike three times and been locked out by management once in the past 20 years, said John Gidwitz, symphony executive director. The San Francisco Symphony walked out for 12 days in January and the Utah Symphony Orchestra struck for nearly a month this fall. Leibowitz attributed the musicians' feistiness to several things, including a belief that they should be compensated for the years they have spent, many since childhood, devoted to their art, and their view that working in the orchestra is a career, not a stepping stone to individual acclaim. ``For us, the big break is to crack a major symphony orchestra,'' said Charles Underwood, BSO violinist. Gidwitz attributed the strikes to a history of inadequate wages that musicians reversed by walking off the job. ``I hope and guardedly believe as musicians start to attain more reasonable salaries we will collectively find less disruptive ways of settling labor contracts,'' he said. Utah Symphony Orchestra executive director Paul Chummers blamed ``unrealistic expectations'' by musicians, who he said don't realize the precarious financial state in which many orchestras exist. The symphony league lists 13 orchestras that are in financial trouble, including Phoenix, Denver, Detroit, Houston and Columbus, Ohio. Chummers said symphonies commonly earn half their costs from ticket sales and depend on donations for the rest. A symphony's labor problems rarely alienate audiences. The Baltimore symphony has not lost community support during the strike, Gidwitz said. Unless a strike lasts the entire season, patrons usually return quickly, Leibowitz said. The Baltimore contract expired Sept. 17. Informal contact between both sides continues but no negotiations have been scheduled. In San Francisco, musicians walked out during the last two contract negotiations, this year and for two weeks in the 1985-86 season. ``Sometimes it seems you need a strike just to get the other side serious about negotiating,'' said Tom Hemphill, chairman of the San Francisco Symphony players' committee. For the BSO, the strike follows four years of harmony between management and musicians _ a relationship that has created a world-class reputation, both sides said. Broadcasting and recording contracts and European tours brought good reviews, and a $40 million fund-raiser recently put the orchestra on sound financial footing. Because of that, the dissonance that creeps into both sides' rhetoric is almost always balanced with at least a token note of respect for the adversary. The 96 players walked off the stage after their Sept. 23 performance, rejecting management's final offer of a $4.2 million, three-year package that would have raised salaries by $25 a week in the first year, from $770 to $795. The union was seeking $1,015 weekly by the end of the 1988-89 season. The orchestra offered $980 by the end of the 1991-92 season, said Richard Hafetz, attorney for symphony management. The union wants to be paid the average of its peer orchestras, including so-called second-tier groups such as San Francisco, St. Louis and Houston. Management said its offer would bring salaries in line with the group, because it totals more than the contract Houston players recently signed. The offer is about $200 less a week than San Francisco musicians earn.