Who was there? Who wasn't ther last night at the White House. It was a full-fledged gathering of who's who in the arts world.

In the foyer: actor/singer Theodore Bikel -- on crutches and just in from Europe -- talking with composer Gunther Schuller.

In a room with blue damask: Joe Hirshhorn, donor of the Hirshhorn Museum, in characteristic bow tie.

In another room: Robert Joffrey, head of the Joffrey Ballet, besieged with questions about the young Ron Reagan, a dancer with Joffrey II. "He's a very nice young man and why don't you ask Tony Bliss," Joffrey was overheard saying politely. Bliss, chairman of the Joffrey board and executive director of the Metropolitan Opera, was also there, somewhere . . . e

In the East Room: actor William Schallert, president of the Screen Actors Guild, tall and stately in dark suit. "You look familiar," someone said. Schallert, ever the gentleman, smiled and replied, "I'm an actor and I used to be Patty Duke's father" (on "The Patty Duke Show").

Walking through the front door of the White House: President Carter . . .

What brought all these people together for last evening's reception, hosted by Rosalynn Carter, was the 15th anniversary of the National Endowment for the Arts and the National Endowment for the Humanities. Among the 600 or so who showed up were artists, arts administrators, a few members of Congress. Some were connected with the formation of these grant-making agencies, and some were not so directly connected.

"Look over there toward the wall," John Jordan of the NEA's budget office instructed a friend. "That guy was the star of 'The Sand Pebbles' -- the one who got the ax in the stomach. He was terrific."

Over by a heavily draped window, Mako Iwamatsu was quietly smoking a cigarette. In addition to being in movies, he serves on an NEA review panel for grant applicants in media arts and design. He said not much has improved for Asian actors these days. "The quality of actors has gone up," he said, "but they're still making films like 'Charlie Chan.' Those should be buried."

Artist James Rosenquist, a National Council on the Arts member, wandered through, glass of wine in hand. "Life magazine has been in my studio photographing a 17-by-46-foot painting I'm working on," he said. "I'm making a middle-aged gesture. It's a man or woman resting on a stack of star nebula . . ."

From the Humanities, scholar Dumas Malone, 84, said a few words. Malone is working on his seventh volume of a biography of Thomas Jefferson, funded at least partially by NEH. "Jefferson believed the world would be saved by knowledge, and it hasn't yet," said Malone, "but it sure won't be saved by ingorance."

And on the political side, it was not a bad crowd, either. "I'm so happy to be back for this occasion," said Lady Bird Johnson, escorted by military aides and mobbed by everyone else. The legislation founding the two endowments was passed in 1965 during the Johnson administration. "At the grass-roots level, arts are flourishing," she said.

Lynda Bird Johnson Robb and husband Chuck Robb (the lieutenant governor of Virginia) smiled in formal dress. "Excuse me," a military aide in white dress said to Lynda Robb. "Your mother wants to see you."

Rosalynn Carter spoke briefly to the guests. "The arts and humanities are flourishing today due largely to the effort of the two endowments," she said. "Think of all the people who've seen 'Lincoln Center Live'. Think how many people saw the King Tut exhibit." Both of those were made possible with help from one endowment or the other. And Mrs. Carter got in a political plug: "I'm very happy to say support for the endowments has increased under my husband."

Actually, Mrs. Carter was more excited about a mental health systems bill that had just passed Congress. She had helped shepherd it through. "I know this is not appropriate to say, but I'm going to say it anyway," she told the crowd, explaining her news. "And I had to tell someone," she concluded.

Her husband swept through later, pressing the flesh. "I've been up on the Hill working with Congress," Carter said, as he made his way through the crowd. (Congress is rushing to finish up this session.) Local scene-maker Steve Martindale guided a friend up to shake Carter's hand. "He's from New York," Martindale said. "You'll need his vote." Carter laughed.

What the president missed earlier in the evening was a rendition of "'happy Birthday" by NEA chairman Livingston Biddle on cymbals, National Symphony Orchestra board member David Lloyd Kreeger on violin and NSO conductor Mstislav Rostropovich on piano.

"Mrs. Carter felt this warranted a performance by three of the greatest musicians," said Kreeger to the guests. "Unfortunately, only one could come So you're all invited to listen and then vote on who that is."