Reprinted from yesterday's late editions

"There are a lot of lovely little meatballs getting cold in there," sighed the young man in pinstripes.

"Oh, but there's never a dull moment with the National Symphony," said his pantsuited friend, making the best of the bomb threat which had routed about 100 guests from a reception before Tuesday night's live television broadcast by the symphony at George Washington University's Lisner Auditorium.

The telephoned threat turned out to be a hoax and some 40 minutes later the reception continued - but with the eating and drinking somewhat accelerated to meet the 9 p.m. air time of the concert. The concert was sponsored by WDVM to promote sales of season tickets for the symphony's 1978-79 season.

Inside the hall, however, further developments had left the concert momentarily in jeopardy, as a frantic search ensued for the trousers of NSO conductor Mstislav Rostropovich. "There were three hangers!" wailed a nervous-looking man with spectacles. "One had the cummerbund, one had the jacket, and one had the pants." Was the Maestro upset? "Oh, no. He doesn't get worried about this sort of thing. He just wants his pants."

The trousers were found, and there remained the biggest surprise of the evening, the appearance of Aaron Copland and Leonard Bernstein to share the podium with Rostropovich in performances of their own compositions.

While the audience took their seats unaware, the two conductors, in town for the gala concert in honor of Bernstein's 60th birthday tomorrow evening at Wolf Trap, strolled arm-in-arm through a side entrance.

"We met in 1937 and decided we'd conduct together tonight," said Bernstein, smiling at his old friend. "You were 33 and I was 16."

"Does anyone here have a baton?" asked Bernstein.

Someone asked Rostropovich how he felt about conducting on live television. "Oh, many years ago, in Moscow, it was all live.It is always better live than . . ." He turned to his interpreter and shot off a bolt of Russian.

"Always better," she translated, "than canned goods."