Traditionally, the Democrats are a noisy, talkative group at their annual congressional fund-raising dinner. They just keep right on talking and having fun as the speakers are speechifying.

They did this last night, too -- that is, until House Speaker Thomas P. (Tip) O'Neill, the big bearish guy with the shaggy white hair, took the podium to bid farewell after 50 years of public service, saying passionately that "America remains the great good hope of those who want to be free."

At that, the 1,700 dignitaries and paying guests fell silent and listened.

Not quite so silent that you could hear a pin drop; but still, they clearly showed their respect for the man who, as Sen. Robert C. Byrd of West Virginia said, "is like no one else . . . a living symbol of the Democratic Party . . . a true patriot and a true servant of the American people."

At the end, O'Neill called his wife Millie up to the podium and, to the cheers of the crowd, announced that they would soon be celebrating their 45th anniversary. Then they embraced one another and the dancing began in the international ballroom of the Washington Hilton.

The $1,500-a-plate dinner raised more than $2 million, according to cochairmen Sen. Joseph R. Biden Jr. of Delaware and Rep. Steny H. Hoyer of Maryland. It was the largest amount in the 23 years that the dinner has been held.

The money will go to Democratic candidates for the House and Senate. Last night the talk was mostly of the Senate, where the Democrats hope to gain control in this year's elections.

"I believe we'll win the United States Senate," said Sen. Edward Kennedy. He said the party has "candidates who are speaking to the issues of concern to people. I believe there's a new activism in the party across the nation, and if we have one-fifth of the money that the Republicans have, we'll control the Senate."

Democratic National Committee Chairman Paul Kirk said he hopes that after the election, "we'll be in the same position the Republicans are now " with a Senate majority of 53-47. But he expressed caution, saying, "It's going to take a lot of work. We'll take nothing for granted, but I think it's coming together."

Several people said that the results of Tuesday's state primaries were encouraging. According to Sen. Howard Metzenbaum of Ohio, the primary victory of Republican Sen. James Abdnor in South Dakota is "good for the Democrats" because Abdnor will be easier to beat than the man he defeated, Gov. William J. Janklow.

Rep. Michael D. Barnes, who is running for the Maryland Senate seat being vacated by Republican Charles McC. Mathias, stopped by briefly. He said he's about 10 points behind Rep. Barbara A. Mikulski, whom he faces in a primary along with Gov. Harry Hughes and Baltimore County Executive Donald Hutchinson.

"We've got three months to go and it's getting very exciting," said Barnes, who left before dinner to campaign.

Sen. Gary Hart of Colorado, asked if he would run for the presidency again in 1988, reiterated his nonposition: "I don't know. We'll decide that after 1986."

O'Neill said before dinner that he thinks his party will pick up 15 seats in the House.

"The Democratic tide is rising," he said.

Later, in his speech, O'Neill attacked "Soviet repression" and racism in South Africa.

He went on to talk of how life in America has improved for most people in the last half-century, praising the Democratic Party's "commitment that the American dream" be a reality for all.

Fifty years ago, he said, "if you were sick, you collapsed." There was "no income for the old . . . Only the lucky few had pensions." Republicans, he said, opposed Social Security.

Fifty years ago, he went on, there were "a few rich at the top and millions of poor at the bottom." He said only 3 percent of high school graduates at that time went on to college, while today the figure is 65 percent.

In short, he said, there has been "a massive improvement . . . in American life," an improvement he claimed was due to the influence of the Democratic Party.

Then they played "When Irish Eyes Are Smiling" and O'Neill waved and shouted, "This is it, everybody! I love ya!"