No sooner does an American president congratulate himself for a sharp rise in the stock market than market prices tumble, leaving the president (I suppose) put out.

But then that's what a president gets for pretending to know something about the stock market. It bloweth where it listeth and no man seeth it.

The longer I sit around here the clearer it is that governments not only do not know quite what they are doing, they also are substantially fuzzy about what they should be doing if they knew how.

A great good government operates entirely with mirrors, as you might say, and if the images come out right, in some attractive way, people say now THERE was a great administration.

The basic daily grind may not have changed much, and the tides of fortune have come and gone as usual, quite beyond control, and like marriage it is all largely a matter of luck how it turns out.

But there are a few things within government control, even within White House control, such as musical evenings, and I recommend we start there.

Of course, the White House has already had musical evenings, some of them presided over by Beverly Sills whose enthusiasm and radiant smile have made her America's darling and whose mere presence is a living breathing blessing in a nutshell. She keeps introducing the stars of tomorrow, some of whom can even sing, and who undoubtedly go home to their agents insisting they are now a hot property, but who are not going to be Kirsten Flagstad, after all, I believe. Especially the ones who do not sing all that well.

But to get on, this is not what the White House should be doing. It should be having an opera festival. There are three operas that sum up opera, and which should be given on succeeding nights:

They are, of course, "Don Giovanni," "Tristan und Isolde" and "The Magic Flute." There can be a matinee of "Norma."

Some will say these are highbrow operas, which is the whole point. It is hardly necessary for anybody to tune in television for the White House telecasts of these admirable examples of the musical theater. Indeed, nobody to speak of will, what with "Plagues," "Kennedy Girls," "Pompey's Vet," "Stuff Your Gullet" and "Glenda Slag" competing for the prime-time ratings.

All that is necessary is to persuade some network to telecast the White House operas in exchange for some small informal favor and some network will.

People like to think the White House is a seat of high culture, and this opera series would do it and it only lasts three nights, after all. It is hard to think of an appropriate hostess, of course, since figures of high culture commonly have manners or mannerisms that would defeat the whole purpose, but I think M.F.K. Fisher would do, if she could be got out of the kitchen and into some silks. Miss Sills could be a gracious usherette.

The same evenings, the president could drop in on additional performances elsewhere in the capital, in order to make the late news telecasts at a more plebeian level.

For the quiche and Brie idiots there should be "Traviata" at the Folger. For the Bud bunch, "Music of the Yukon" at the National.

The president would show up everywhere, on these three nights, taking care to be in his seat at the intermission of "Don Giovanni," with a handkerchief in hand, greatly moved.

Tweed-bearing types would gather at the British Embassy for "Pinafore," which they have got the hang of by now, and for those who get confused if anything goes very fast there should be "Boris Godunov" under the gracious patronage of the Soviet ambassador. Ethnics ought to have "My Fair Lady" or "West Side Story" or something of the sort outdoors in Adams Morgan and all those people who never quite get in to the capital would rejoice with "The Student Prince" at Wolf Trap. Thus everybody would be satisfied.

Nobody should argue that the president would have to do a lot of hopping around for these three nights. If there is one thing any White House is good at, it's arranging transportation. Others, I know, would say an American president cannot afford to take three nights away from his heavy burdens. To them I say come off it.

For the image to be firmly fixed, and for the project to be a great success, it truly is important for the high culture to be at the White House. This will not offend people. As long as they aren't expected to enjoy it, people think very well of Mozart and Wagner. The unwashed have nothing against magnificent bathrooms, after all. "Don Giovanni" is just not their thing.

They like to think--or they would like to think if they had an excuse for thinking so--the top of the line is going on at the president's house.

Of course, you'd want to watch out for too many Italian-type guests that might remind people the thing is in Italian. graphics: People like to think the White House is a seat of high culture.