The Kandinsky exhibit opening today at the National Gallery of Art is small (about 30 pictures) and limited to his improvisations (which he actually mapped out rather well before he painted them), but Kandinsky's works can be powerful. Ask Librarian of Congress Daniel Boorstin.

He was standing in the gallery's cool, elegant board room with NGA Director J. Carter Brown and Soviet Ambasador Anatoliy Dobtrynin (Kandinsky was Russian-born). The lunch was for curators, lenders and interested aficionados.

"We owe a lot to Kandinsky," said Boorstin to Dobrynin. "My wife and I courted at the Kandinsky exhibit at the Guggenheim in 1942." Ruth Boorstin nodded.

Dobrynin considered this for a moment, pausing to eat a canape. "Nineteen fourty-two! We were courting then, too," he said with enthusiasm, nodding to his wife.

"It was in an aviation factory. We were building airplanes! We are engineers."

Talk turned to scholarship, and Boorstin, wearing a blue bow tie and yellow shirt vaguely reminiscent of Kandinsky's most inspired palette, mentioned the library's new council of scholars.

"But Washington is such an impatient city," said Dobyrnin. "Always demanding results and immediate answers."

"Well, Mr. Ambassador," answered Boorstin, "with all due respect, I must remind you of your own county's five-year plans."

The ambassador thought this was very funny.

The only Kandinsky in the National Gallery's permanent collection (No. 31) hapens to be in mint condition, having been bought by a Swiss sewing machine heir who decided he didn't like it and them hung it in his wine celler from 1916 to 1878, said E. A. Carmean, the curator of the 20th-century art. Guess Who's Late to Dinner?

Gore Vidal took his time getting to the party Nancy Dickerson gave to celebrate Nina Straight's book, "Ariabella the First." As the evening wore on, his absence became the main topic of conversation. It's just like Gore to plan a party and not show up," said Val Cook, the Saks Jandel fashion wizard who knew him in Rome.

AFI mogul George Stevens Jr. buttonholed Charles Wick over near the fireplace. Wick is the Reagan administration nominee for director of the International Communication Agency.

"Still going through confirmation?" asked Stevens.

"The confirmation hasn't even come up yet," said Wick. "I'm hoping sometime in April."

Had Wick read the book? someone wanted to know. "No."

Did he know the plot?

"What is it, a novel?" asked Wick. "Frankly, I think they ought to print synopses on the invitations."

But alas, there were no synopses. Thee weren't even any copies of the book except one that belonged to Jamie Auchincloss.

"No, no copies of thebook here," said Wyatt Dickerson, Nancy's spouse, the squire of Nerrywood. (Merrywood is the Northern Virginia estate where Vidal as well at Auchincloss, Straight, Jackie Onassis and and Lee Radziwill spent time growing up. They're all related, somehow.) Vidal arrived late, clambering out of a Red Top cab with valises in hand. But no books.

"Jamie just left with his copy," Wyatt Dickerson volunteered. "I think he's selling it at the top of the driveway." Stranger Than Fiction

Writer Warren Adler has a new novel, too, "The War of the Roses." Adler goes to lots of parties because his wife is the guiding light of Dossier magazine, the compleat chronicle of the glittery comings and goings of social Washington. "I write during the day," said Adler, "And I go to parties at night. It's perfect."

He had a publication party, too and was generous with synopses, to wit:

"The Roses are a couple. They live in a house in Kalorama Circle. They have everything. But she wants out of the marriage. He says, 'Okay, I'll give you half of everything I have.' She says, 'No, I want everything.' So they stay together -- under the same roof -- and they tear each other apart.

"And you know what? Everyone in this town thinks I wrote it about them." Ask Me No More Questions

The Syrain National Day celebration at the Washington Hilton was peopled with Syrians, Lebanese and various Washingtonians who go to that sort of thing.

Three such men were standing near the bar, one from the State Department office of protocol, one from the Woodrow Wilson Center and one from the Embassy of Pakistan.

"Diplomatic relations are parties where only high matters of state are discussed," said the embassy officer. "That's a secret."

"But no surprise," said the State Department man.

Yamaha, the Japanese company that brought you pianos and organs (to say nothing of motorcycles), is also in the business of teaching young people to play. There are 6,000 Yamaha music schools in Japan alone. And last Monday, six of the Yamaha prodigies wowed Washington.

It all started sometime back during a National Symphony tour of Japan, when Mstislav Rostropovich heard some of the young musicians and was sufficienly impressed to invite a group to the United States. The program at the Kennedy Center Concert Hall Monday night included the children's works, orchestrated by none other than the maestro himself.

The Japanese ambassador didn't stay long at the post concert reception at the Watergate Terrace Restaurant, but Deputy Secretary of State William Clark did, acting as the evening's ambassador of good will.

"I want you all to sign this program for the president, who wanted very much to be here," he told the soloists, and then invited them over to the State Department.

Ten-year-old Rie Yoguchi, of Tokyo, sat at a table with her cohorts, who were devouring French pastries. Wearing a white dress and well into her second Napoleon, Yoguchi paused politely to answer some questions.

Yes, she was having a good time, said her interpreter.

Her favorite composers?

"Chopin and Schumann."

"She says she liked the Japanese cherry blossoms very much." Roll Call

The American Society of Newspaper Editors convenes every year to discuss business, socialize and catch up on industry gossip.

"We stayed late at the party," said Anthony Day, who's with The Los Amgeles Times. He and Charles Bailey, the editor of The Minneapolis Tribune, were members of the Washington press for years and now consider them "parolees."

"It was a great party," said Bailey of a pre-opening session party. "Real Washington. People kept running up to us and saying, 'Hey, great to see you!' Then they'd see someone over you should and disappear."

"We sang gospel music with Jody Powell," said Day. "Bringing in the Sheves,' and 'When the Roll is Called Up Yonder.'"

"Jim Schlesinger sang, one," said Bailey. "He's tone-deaf."

"Jody's an old gospel singer," Day continued.

"He sang the words before us," said Bailey.

"Just like Jerry Falwell," said Day.