Utah Symphony musicians were back at work Wednesday following settlement of the longest strike in the orchestra's history.

The settlement came Tuesday, following afternoon meetings between union and management negotiators. Later that evening the musicians voted 73-10 to accept the proposal approved by the symphony board Monday."The contract we have signed is not a satisfactory one," said union spokesman John Thompson at a press conference at which the three-year pact was initialed. He went on to call it "a tremendous compromise on our part. The Utah Symphony musicians will not be catching up to comparable major orchestras in the next three years."

Nonetheless, it was hard to think the musicians had not obtained most of what they had sought, namely:

_Retention of the 52-week season and an 83-member orchestra. Until two weeks ago the management had asked that the season be reduced to 46 weeks and the number of players to 75.

_Salary increases every year for the next three years, beginning with 1.9 percent in 1988-89 then moving to 3 and 7.4 percent in the years to follow for a base pay of $31,629. Previously the management had insisted on a reduction the first year of 3.7 percent.

_Seniority pay in the amount of $5 per week for each 5 years of service.

_Medical insurance for all musicians and their dependents at no cost to the musicians, together with long-term disability coverage.

_Elimination of the service-conversion agreement under which Utah Symphony recordings have been made since the Abravanel era. Henceforth, recording sessions other than concert broadcasts will have to be paid at union scale.

"This has been a very painful process for all of us," said board chairman Deedee Corradini of the strike, which began Sept. 1. "Now the time has come to get together as a team . . . and do everything we can in the next several years to raise the money to support it."

Although neither side was willing to discuss the cost of the strike, the four-week work stoppage is estimated to have cost the musicians about 10 percent of their annual salary in wages and lost benefits. By the same token the six concerts that had to be canceled - one of them a benefit for the orchestra - together with lost revenues from the Ballet West opening may have cost the management as much as $170,000. Against that must be measured an estimated $180,000 savings in salaries.

Corradini said she was apprehensive about the amounts the board is now committed to raise. In recent years nearly $2 million of the orchestra's $5- million-dollar annual budget has had to come from contributions, an obligation the current contract increases by as much as $700,000.

"I'm scared to death," she said after the meeting, "but I feel we've got to do it. It's now or never." At the same time she emphasized the orchestra would need help in both its annual fund drive and upcoming endowment campaign.

Thompson added that the musicians will do everything they can to participate in fund-raising efforts.

The only previous strike in the orchestra's history occurred in 1983 and lasted five days.