AT one of Sid Yates's hearings, celebrated cellist Yo-Yo Ma showed up and played an unaccompanied Bach partita in the hearing room. Representative Yates, an Illinois Democrat, is used to that kind of music from his constituents, because he chairs the powerful House appropriations subcommittee on the Interior, which decides on money for the arts. When the President's budget hits the Capitol steps next week with a thunk like a bale of Sunday New York Timeses, Sidney R. Yates will be ready. He'll tunnel through to the section on the National Endowment for the Arts to find out whether the administration is proposing an 11.7 percent cut in the arts budget, as leaked, or 40 percent as it tried to in 1981.
Either way, Mr. Yates is braced for a debate that makes Tchaikovsky's ``1812 Overture'' with its cannon salute sound like ``Clair de Lune'' in comparison. Congress loves culture and has regularly battled the administration for funds, even if the debates have been, as Yates says, ``pallid in comparison to British debate or the way ours used to be in the old days.'' He tells this story to illustrate:
``There was an encounter between Henry Clay and John Randolph on one of the muddy paths of the Capitol. This wasn't an example of parliamentary debate, but it was a matter of rhetoric. They were on this narrow path over the mud. And they were bitter enemies. They glared at each other for about 30 seconds until finally Randolph snarled at Clay and said, `I never make way for scoundrels.' Clay stepped aside and bowed and said, `I always do.' ''
For supporters of the arts, any cut in the arts budget signals ``scoundrel time,'' in Lillian Hellman's phrase. This year President Reagan is asking only $144.5 million for the arts, according to a New York Times story that previewed the endowment budget. That figure, if accurate, would be sharply down from the $163.7 million Congress appropriated for this year.
The biggest cuts would come in opera and musical theater, which would reportedly be cut by 18.3 percent; the music program, by 15 percent; and dance, 13.5 percent. Congress has consistently appropriated more for the arts in the last four years than the Reagan administration has asked, but this year the arts may be pared like an apple. When top Republicans like Senate majority leader Robert Dole are talking of cutting even the Pentagon budget, can the arts be far behind?
``I don't think so,'' says Sid Yates. ``I think it all depends on the size of the cut. It depends as well on what's happening to all the domestic programs. If all the domestic programs are cut, I don't think the arts will be an exception. We haven't really seen the budget yet.''
Yates says that ``when you talk about what you're looking for in the arts budget, it can't be taken out of context.'' Does he expect the cuts could go as high as 44 percent? ``I don't think he'll do that again, not after the last year, when OMB [the Office of Management and Budget] recommended $143 million. My impression is he might go to that figure again. It's hard to say. [Budget Director David] Stockman is not one of my confidants.''
Yates is asked which of the arts is in trouble. ``My own impression is that theater and ballet are suffering the most. All of them are suffering deficits. We won't know what condition the arts are in until [the head of] Endowment appears before the committee to tell us.
``If the Times prediction on what happens to the arts is sound, then the budget would provide for an inordinate cut in music and musical theater . . . because together they're suffering a 331/3 percent cut.''
Yates's prowess in battling for the arts in Congress is legendary. Asked the secret of his success, he murmurs modestly, ``I was fortunate to find a very supportive constituency in the Congress.'' Why? ``Because the arts are very much appreciated through the country. The arts are not only the exclusive province of the urban communities or of rich people, as used to be the case years ago. With the impetus of the National Endowment, the value, the benefit, and the popularity of the arts have gone through the entire country. And I think that's reflected in the attitudes of the members of the House and the members of the Senate.
``Mr. Reagan is the first President who really did not support the arts. The appropriations for the arts had consistently increased with each administration.''
``I've never really understood why he did [cut] it. I think perhaps he was given a total budget with an accumulation of cuts and none of them was singled out. I think he probably approved it on that basis. I know that Stockman knew about it because I interrogated him about it.
``And you remember his black book when it first came out in 1981, when he said that there was no reason for federal support of the arts or of the humanities. He said that. As a matter of fact, I'm reading a book now that says that.''
Yates has been sitting for this interview at a round, walnut table, the kind you gather around for dinner, in the middle of his Rayburn Building office. He gets up, browses through his books, and comes back with Edward C. Banfield's ``The Democratic Muse,'' done as a study for the 20th Century Fund. ``His contention,'' says Yates in a mellow but astonished voice, ``is that there's no justification for federal support of the arts! There is a school of thought on that. I don't happen to agree with it.'' There are clues to that.
On the wall at Yates's left hangs a striking color photo of the painter Georgia O'Keeffe, inscribed to him. Behind him is a huge abstract tapestry, in shades of purple, olive, gold, and orange, one of the Suzannis he collects. In his anteroom hangs a witty Magritte print of a poet in a bowler ``recomposing'' a lavender and peach sunset; the sunset reappears on his back. Small reproductions of works by Hans Hofmann and Morris Louis hang on another wall.
He and his wife collect art, he mentions, ``some but not a great deal'': some abstract expressionist paintings, lithographs by Giacometti, Picasso, and Braque, as well as African, Micronesian, and pre-Columbian art. He confesses to having a big classical-record collection, loaded with Mozart even before he saw the film version of ``Amadeus,'' which he loved.
His favorite Mozart work: Piano Concerto No. 21. When he reads, says Yates, he often rereads classics from Dickens and Mark Twain and current writers like Saul Bellow. He's a skillful writer himself, who turns out literate and amusing newsletters.
If you didn't know he was a congressman from Illinois, you'd guess Sid Yates might be a college professor: quick brown eyes in a thoughtful face, silver hair, a casual but incisive manner. He wears a plain loden green jacket, white shirt, red sweater-vest, black knit tie, greenish-gray trousers, brown shoes.
As chairman of the committee that determines the budgetary fate of the arts, Yates often hears testimony by a parade of stars.
``One of the real delights of this position is having the opportunity to exchange views with some of the great artists of the day,'' he says with a smile. Among the ones he ticks off: actors James Earl Jones, John Houseman, Jane Alexander; opera stars Ris"e Stevens, Sherrill Milnes, and maestro James Levine; and performers like Yo-Yo Ma. Yates notes that corporate and private support of the arts and humanities is on the upswing -- $4 billion in 1983. But he has some reservations that corporate giving stifles innovative, experimental, and possibly controversial programming.
``And that's one of the advantages of the federal government, the fact that thus far at least Congress is willing to stay out of exerting any influence as far as programming by the national endowments or the experimentation they undertake or approve. Somebody has to do that, otherwise the arts would remain quite static.''