Karl Boehm and the Vienna Philharmonic brought the Blue Danube to the Potomac last night -- almost upstaging the other star of the evening, Austrian Chancellor Bruno Kreisky.

The waltz from "The Beautiful Blue Danude" was an unscheduled encore; Kreisky was a scheduled honored guest. He and his wife, with Austrian Ambassador and Mrs. Karl Herbert Schober and Rep. Clement Zablocki (D-Wis.), chairman of the House Foreign Affairs Committee, occupied the presidential box at the Kennedy Center on the Austrian national holiday.

Kreisky's Washington appearance had some political overtones. He met yesterday with President Carter and Secretary of State Cyrus Vance.

Last night at a post-concert reception for 800 guests in the Center's Atrium, Kreisky said, "We had a conversation about everything."

Did that include the Middle East?

"Everything," Kreisky said, decling to elaborate.

Would he be meeting again with the Palestine Liberation Organization as he had in July when he unofficially entertained Yasser Arafat at a reception in Vienna to the chagrin of the Israelis?

"It depends . . . "Kreisky said.

The reception was given jointly by the Kennedy Center, the Viennese ambassador and the Vienna State Opera, which gives its opening performance tonight.

Before the concert began, Kreisky joined a gathering of the Music Critics Asssociation which is holding its national meeting here. Ushered through the room by the Center's Martin Feinstein, the chancellor shook hands with most of the more than 100 music critics present.

"Some critics I do not like," he said, "but I am very glad to see so many music critics here -- because I know they will not write about me."

"Unless you try to sing," warned Feinstein.

In the post-concert crowd was U.S. Ambassador to Austria Milton Wolff, former ambassador to Austria Wiley Buchanan, the Ralph Deckers, the Tazwell Shepards the William Cafritzes and most of the 120 members of the orchestra.

In the grand old tradition of carrying coals to Newcastle, menu planners had arranged to serve Wiener schnitzel and apfelstrudel.

"We eat it rather often in Vienna," said Clemens Hellsberg, violinist. "But this is Wiener schnitzel in Washington."

In another grand old tradition, Kreisky made a promenade of the room. In the crowd the encountered noted Viennese jeweler Edwin Haasman, whose firm opened a $10-million jewelry exhibit at the Watergate this week to coincide with the arrival of the orchestra and opera.

Maya Haasman was wearing some of the merchandise, which her husband estimated to be worth about $150,000. Haasman said he made a couple of little presentations to commemorate the occasion earlier in the week. One was a sapphire ring for Mrs. Boehm: "Friendship," he said, "has no price." The other was a Liberace-like gold and ivory baton set with rubies and diamonds presented to Leonard Bernstein, who told Haasman he will use it when he conducts the Philharmonic here tonight.

"Anybody can live the usual way," said Haasman of his castle in Salzburg and his generous style, "I like to go through life in an unusual way."