Just after 1 a.m. yesterday, Sen. James A. McClure (R-Idaho) conducted a bedraggled band of senators through a symphony to the John F. Kennedy Center for the Performing Arts: forgiveness of multimillion-dollar interest debts to the federal government.

In a matter of a few minutes, McClure persuaded the Senate to agree to add his amendment by voice vote to the continuing resolution to keep the government operating for the next fiscal year. It would excuse the center from paying $33 million in past interest and free it of interest payments for the next 33 years.

Sweet music for the center, perhaps, but Rep. Guy V. Molinari (R-N.Y.), who, like McClure, bills himself as a fiscal conservative, was fuming.

"It is a rather sad episode," Molinari said, "and Sen. McClure is going to have to answer for his own actions . . . . How do we, with all the rhetoric and nonsense over deficits and a balanced budget, justify this in advance -- a total giveaway?"

"We're going to make a last-ditch attempt to stop this, but if it passes, it means that they're going to get a great big gift . . . . This bill has been wired -- it has support from both sides of the aisle and the administration," he added.

Molinari's chances of derailing the Kennedy Center legislation appeared slight. The language will be subject to challenge by House delegates to the House-Senate conference that will work out differences in the bill. Molinari was worried that he and Reps. Clay Shaw (R-Fla.) and Gerald B. Solomon (R-N.Y.), his chief allies, would not get their message across.

The center's debt stems from the government's help in building a parking garage. The debt was to have been repaid through revenues, but income has not matched projections and the center is far in arrears. Its officials want off the hook.

Molinari said he had proposed a compromise that excused past interest debt but required future payments, even though "I was not terribly proud of it, but it was the best we could get." But his compromise never got out of the House Public Works and Transportation Committee, he said.

The New York congressman charged that center officials had reneged on a deal to accept the compromise, then went behind his back and dealt with "special friends" on the Senate side.

"They became pigs and said they had friends on the Hill who could solve this for them . . . ," he said. "I'm frankly outraged and they're going to be hearing from us in the future."

For reasons no one can figure out, the final days of this Congress, though drawn out (the Senate didn't quit yesterday until after 2 a.m.), seem devoid of the customary wild hurly-burly.

In fact, aside from a reservoir of bad feeling over the conservative-led derailment of civil-rights legislation, there's a lot of sweetness and light.

The usually taciturn Rep. Jamie L. Whitten (D-Miss.), dean of the House and chairman of the Appropriations Committee, took the floor yesterday to say how good he felt about the nice things that have come his way lately.

A week or so ago, bending its rules a bit, the House agreed to name an agricultural experiment station in Mississippi after Whitten. Then his portrait was hung in the Appropriations Committee.

In another gesture of good feeling, the Senate agreed to add $4 million to the continuing resolution to help finance creation of a Peace Academy, an idea that Sen. Jennings Randolph (D-W.Va.) has promoted for years. Randolph is ending a career that began with his election to the House in 1933.

Remember Sen. Howard M. Metzenbaum (D-Ohio), whose objections to last-minute legislative sweeteners have become legendary?

Well, early yesterday, just before McClure helped out the Kennedy Center, Metzenbaum got the Senate to agree to a reallocation of money to restore the William Howard Taft birthplace in Ohio. "It's not new money," an aide said.