Symphony orchestras across America have been in deep trouble during the past year, afflicted with strikes and lockouts, struggling to raise money, and in some cases canceling seasons and even declaring bankruptcy.

These are not so much the top-level ensembles of the largest cities, but rather orchestras in the American Symphony Orchestra League's "regional" category, with annual incomes of $1 million to $3.6 million _ orchestras like Oakland Symphony (bankrupt), San Diego Symphony (cancelled season), Columbus Ohio (on strike) and Tulsa (locked out).Orchestra officials and union negotiators around the county suggest the following explanations for overall orchestral insecurity:

A collapse in too-rapid growth over the past decade, as middle-level communities realize they simply cannot afford a fulltime ensemble; symphony boards insisting on new toughness in labor negotiations; greater difficulty in fund raising, caused by government and foundation cutbacks, declining oil prices and increasing corporate takeovers; and uneasiness of both management and musicians that orchestral music itself may be in trouble, with shrinking discretionary income and declining arts education cutting off future audiences.

Other orchestras that have suffered long strikes or obtained wage freezes or concessions in the last year include those of Honolulu, Denver, Sacramento, Phoenix, Oklahoma City and Houston, as well as the Florida Orchestra, which serves Tampa, St. Petersburg and Clearwater. San Diego, Denver and Houston fall into the league's "major orchestra" category, with incomes over $3.6 million.

In 1975 there were 16 regional orchestras in the U.S.; today there are 39, reflecting the desire of communities to offer an attractive amenity; but the fundraising effort is often greater than symphony boards expect. Many such orchestras are badly undercapitalized. When orchestras move from night services to day services and players cannot hold other jobs, their demands increase, and what boards are able to pay may not be enough to live on.

Union demands have not been excessive; in many places, players have ratified wage rollbacks. Meanwhile, symphony boards are showing a greater tendency to deal with realities. "Boards are taking a tough stance because they see other orchestras going out of business or running huge deficits," said Nancy Sies, executive director of the Tulsa Philharmonic. "Musicians will only be secure if the orchestra's finances are secure."

Corporate takeovers have likewise affected donations to the arts, as regional companies are absorbed by corporations in faraway cities. (The Western-Delta merger is a local example of such loss to the arts.)

The graying of American audiences and the effect of increased sophistication in audience demand, brought about by listening to recordings of first-rate orchestras, are also concerns among local orchestral promoters.