LET'S BEGIN with a pop quiz, shall we? Has your newspaper ever told you exactly how many of your state legislators are lawyers, and how many have represented utilities or insurance companies that they are supposed to regulate by legislation?

Or has a TV newscast ever explained to you just how the oil companies do their accounting, so that you can critically judge their claims, in paid ads, that they don't make obscene profits, but in fact net only pennies on the dollar?

Or have you read in your favorite magazine or paper a clear outline of its own strategy of survival? Has it helped you, through defining such terms as "advertising cost- per-household" or "demographics" to know why you've got fewer choices at the newsstand than your father and grandfather had?

Or have you heard any broadcasts describing exactly how "trade associations" keep tabs on what congressmen and federal agencies are doing that might affect their profits? How much money they spend on protecting their interest--which may or may not be yours? I'm not talking about anything as crude as Abscam, now; just your day-in-day-out big-lobby operations. Do they fill much airtime?

The answer to all four questions is almost surely no. That's a fact which troubles Ben Bagdikian, and which should trouble you, too. His book is strong and controversial stuff, but it's no simple muckraker's cry of outrage against some "conspiracy" to keep you ignorant of how great corporations use and abuse you.

The problem, as he sees it, is institutional, not personal. The media themselves are becoming part and parcel of the small group of powerful conglomerates dominating our economy. They belong to the system that they're supposed to cover objectively on your behalf.

That's one danger to freedom of the press. The other is that mass advertising forces a change in the substance of the news itself, encouraging the presentation of more non-upsetting, bland material that won't spoil the euphoric, self-centered mood that encourages consumers to the sweet buy and buy.

Now, a review of medium length can't reasonably summarize or rebut Bagdikian's evidence. Suffice it to say that he does present some grim figures. Twenty corporations control more than half the 61 million daily newspapers sold every day. Twenty control more than half the revenues of the country's 11,000 magazines. (The term "control," as we'll see, is a bit tricky.) Three networks divide most of the television audience and advertising revenues among themselves. In book publishing the number of monster/master corporations is 11; in motion pictures, four. Since some of these overlap, there are in fact only 50 corporations whose presidents hire and fire the people responsible for presenting news and ideas to 220 million Americans.

And more, the media-owning corporations have other industrial interests ranging across the board. Paramount Pictures and Simon and Schuster, for example, are part of the Gulf p Western empire, whose satrapies include makers of cigars, pantyhose, sportswear, microprocessors, tankers, and jet engines.

And still more. Directors of the media corporations sit on the boards of still other conglomerates, so that through these interlocking directorates, the makers of public opinion on such matters as taxation "are partners in . . . agribusiness, airlines, coal and oil, timber, banking," and many other industries such as video games, telephone systems, weapons production, frozen foods, rocket engineering and plastics. "This is more than an industrial statistic," says Bagdikian. "It goes to the heart of American democracy."

Meanwhile, concentration marches on. Magazines go under because they can't deliver as many households per-advertising- dollar as TV. "Inefficient" units in the newspaper world are merged or dropped. The big survivors eventually become sole survivors. The one-paper or one-ownership town emerges as the norm, protected by law from antitrust regulation. The publishers and TV-station owners, who sing the praises of free competition as against socialism, nonetheless defend monopoly in their own business and snap up new competitors like cable TV. They insist that "product"-- i.e., the news--doesn't suffer. In fact, it does. There's less of it, with less bite, and what there is--in print or on screen--increasingly addresses the concerns of the "upscale" readership sought by the marketers. The offerings become homogenized and boring. The audience grows apathetic and, like the electorate, begins to shrink.

Thus runs the indictment. What of the responses? There are many that can, and undoubtedly will be made. Bagdikian himself notes some.

First, there's still a "saving remnant of diversity" outside the control of the dominant 50 (like the Beacon Press, which is publishing this book). Next, working journalists today are better educated, more sophisticated and probably more conscientious than the old-timers of a half century back (though we see them imperfectly through a number of romantic memoirs).

Furthermore, "control" is hard to prove. Directors rarely know or want to know what's going on operationally in the companies they "supervise." Corporation presidents generally leave hiring and firing to the professional managers who run their media subsidiaries. They read the bottom line and that's all. Bagdikian comes up with only a handful of examples of heavyhanded intervention. One of those, in book publishing, backfired on him. His sources at Simon and Schuster did not confirm his version of the alleged killing of a manuscript that carried the title of Corporate Murder.

And anyway, publishers and TV executives eventually do pick up on stories of corporate misdeeds--defective cars, dangerous additives, polluted waste dumps. They do so with enough frequency to irritate their supposed corporate masters. The title, "media monopoly," in fact, has usually been used by conservatives denouncing "liberal" domination of the news through their supposed influence in the major networks, The New York Times, and The Washington Post.

And didn't the media give an enormous boost, through publicity, to the egalitarian revolutions of the 1960s? It may have been only an editorial fad, but gains were made and gains have lasted even after new versions of news chic have chased the firebrands off the front pages and the air.

In the end, then, a debater could argue that Bagdikian, shooting wildly at too many targets, is making a great to-do about a problem that is less grave and more self-correcting than he acknowledges.

But it would be a shame to leave that impression; to dismisss The Media Monopoly with a lukewarm endorsement and a tut-tut. At root, Bagdikian is sound. The proof is in the product, as anyone with a smattering of journalistic history knows. Papers were far zestier in de Tocqueville's day, when any middling sized town boasted three or four of them, owned by the same men who got them out daily.

Early big-city press barons like Bennett, Pulitzer, and Scripps were cranks and scolds, who delighted in tweaking the noses of bankers, politicians and fellow- capitalists. They said that their first duty was to protect their readers from the greed of the wealthy and they damned well meant it. The muckraking magazines of S.S. McClure's short turn-of-the-century heyday hammered away in issue after issue--not just occasionally--at the treason of the Senate, the shame of the cities, the bitter cry of the children. (Until, as Bagdikian demonstrates, the bankers began to call in the publishers' notes to shut them up).

We've nothing comparable now. Not even the most liberal columnist challenges the fundamental premises of American capitalism, or the American foreign policy aimed at preserving it. That's the job of radicals, and where are they represented in media management? Nowhere. That dissonant chorus that makes the music of democracy--that Babel of populists, singletaxers, and greenbackers, of socialists, communists, anarchists, fascists and feminists, of libertarians, vegetarians, free lovers, and free traders--you don't hear it on the airwaves or read its lyrics in newsprint. The media are in the mainstream, and what floats on their current is flotsam and jetsam--sitcoms and Superbowls, comic strips and recipes, and precious, precious little serious analysis or examination of what comes out of the mouths of elected officials or the public-relations departments that furnish much of our so- called business "news."

A few major papers partially escape this generalization. But if you travel much, you know it's true for most of the 1,730 U.S. dailies, which are largely boilerplate.

Surely, Bagdikian is correct in saying that these sad developments are not unconnected with corporate domination of the media. Or that control from the top is exercised, even though subtly and by implication, to dampen stories that will unduly upset the bosses.

Yes, there are many other reasons, going deep into modern history and technology. Nor can we unravel the technological web that has given us our corporate economy or go back to the hand press and the crossroads town any more than we can to the spinning wheel and the buggy. But we can and must find ways to give our problems more substantive and enduring media atention than they get, except for an occasional outburst of irrepressible scandal.

Bagdikian has some very specific suggestions that he believes would help, such as increasing the number of competing voices by limiting cross-ownership of media outlets or by restricting the size of media corporations. He admits that such theoretical rules have flaws that would be exposed in fair discussion. But he doesn't believe, given the nature of things, that such discussion is likely to take place in the media outlets themselves.

Every once in a while, this country gets itself into a position in which we seem to have outrun our capacity for self-rule--a burst of growth so fast and unpredictable that the old machinery, never perfect to begin with, is far out of synchronization. The 1840s were such a period. So were the early 1900s. And the 1930s. We're in one of those eras now, badly needing to incorporate the revolutions of the last 40 years or so into the democratic framework. If we can manage it at all, which isn't certain, we'll need more help than we're getting from the media. Bagdikian may not be 100 percent correct. But if he's only 90 percent right--or 80, or 50, or 20--he deserves to be heard and pondered. His book could be of profound importance in the 1980s and beyond.