IT IS here at last, after years of advance techno-hype and extensive marketing in Japan and Europe: Superdisc--smaller than a 45-rpm record, faster than a speeding microgroove, able to leap 90 decibels at a single bound.

Yes, but who wants it?

Wait, first you have to know what it is. The digital disc or compact disc, rotating at a speed of up to 500 rpm, stores an hour of high-fidelity sound in the kind of space that once was filled by a pop single. It is the audio wonder of the 1980s, and now that we can hear it, the enthusiastic reports from overseas seem substantially true.

Yes, but what makes it so special?

The compact disc does not develop the pops and clicks that are the fate of vinyl records we have loved not wisely but too well. It has none of the hiss that plagues the tape medium. It sounds great, and in its little plastic box (complete with a mini-booklet of program notes), it should be easier to store than a tape cassette.

Yes, but how does it work?

Made of a very thin sheet of aluminum encased in transparent plastic, it carries a microscopically small binary code, not unlike the bar code that now checks out your purchases at the supermarket. This code conveys not the price of your can of beans, but Beethoven or Mahler--in sound that is cleaner and more accurate than any in recorded history. It embodies neatly a totally new concept in the science of sound-recording.

Yes, but who will buy it? Who will buy it particularly at $20 per disc?

The compact disc is a lifetime investment. Handled with reasonable care, it should last as long as you do and continue to give the same sound years from now that it gave the first time you played it. It is decoded by a little playback unit--no larger than your toaster-oven--that will plug directly into your high fidelity system with no fuss and start working immediately.

Yes, but who needs another audio gadget? Who needs it particularly at a cost of $800 to $1,400 per playback unit?

The technical challenges have been met; computer technology has been wed to sound-recording technology, and an opera or string quartet can now be stored and retrieved as a series of binary numbers. The product has been made almost foolproof; a child can play a compact disc much more easily than the standard LP. All that remains to be done technically is detail work, refinements, mopping-up operations.

But a nagging question remains: will the compact disc survive and become the standard format for recorded music, or will it go the way of quadriphonic sound and the dinosaur?

Nobody knows, but everybody has a guess. The guesses tend to be heavily influenced by institutional affiliations.

"It's too early to say," says the owner of a small, high-quality record company that cannot get into the compact disc marathon and may be trampled to death by it. "First, all the crazies will get it because it's new, then the semi-crazies because they always follow the crazies. But I have heard demonstrations and I heard problems; there were some things being played that we would not put out on our label because they don't meet our quality standards. A lot of it was good, but it was not really better than you can do on a standard disc with DBX noise reduction--and you know what happened to DBX; it bombed. It has a cult following but no mass market. DBX should have caught on, like the elcaset and quad and metal tape; they all had their strong points and none of them broke through to the mass market." He asked to have his name withheld because he does business with companies involved in compact disc technology. Perhaps also because he called his own customers "crazies."

These remarks may reflect some sour grapes, but they also reflect solid audio history. The simple fact is that only a small proportion of the market for recorded music is an audiophile market that insists on state-of-the-art sound. Audiophile records do not go platinum, and most people could get better sound from the records they own if they were willing to invest in $250 cartridges (which some diehards still call "needles") and $1,000 speaker systems. Usually they know it, and they don't seem to care.

"We feel that the superiority is so obvious that the compact disc will ultimately make the black disc obsolete and eventually the cassette," says Emiel Petrone in Los Angeles. Petrone is Polygram's coordinator of compact discs--production, marketing, packaging and long-range planning--for the United States.

Polygram is the international giant--including the Philips, Deutsche Grammophon and London record labels--that dominates the classical recording industry. Polygram has an inside track on the compact disc, because Philips (which also originated the tape cassette) was the disc's primary developer, in cooperation with Sony in Japan. Development cost was $400 million. One advantage of this investment is that Philips and Sony have been able to hit the American market first and at the lowest prices--$800 for the Philips player, which is marketed in this country under the Magnavox name.

At the most recent consumer electronic show in Chicago, every major audio manufacturer had a compact disc unit on display but few had units available in marketable quantities. Most audio specialty shops in Washington are selling a few brands (Denon, Sony, Kyocera and NEC are among those at least occasionally available, with Yamaha apparently about to make its appearance), but shoppers may have to hunt around and perhaps wait a while if they insist on having a particular model.

The big exception is Philips/Magnavox, which got in on the ground floor with the most coherent marketing strategy. Players are being marketed in 24 major department stores across the country, with each store enjoying, for the present, exclusive marketing rights in its area. For the Washington area, the store is Hecht's. It is selling them at four locations (downtown, Montgomery Mall, Tysons Corner and Towson), and it is displaying and selling the players (for $800) together with Polygram discs (for $19.95). Unlike other merchants, Hecht's enjoys an unlimited supply of the units as well as the lowest price. The price advantage for Magnavox (and Sony) is probably permanent, since other manufacturers will have to pay a royalty to these companies, which developed the units.

Dick Berndt, Hecht's buyer, reports that in the first month of marketing, the players have sold reasonably well but not spectacularly. "There has been a lot of interest, particularly among audiophiles--people who already have excellent and very expensive equipment in their homes. We have not sold vast amounts, but we did not plan or expect to. We like to be a trend setter, the first ones to have the newest things, and we have customers who are somewhat status conscious and like to see the new things." He expects that in the long run, if compact disc players become an established part of the market, Hecht's will be marketing the products of its regular audio suppliers--Fisher, Pioneer and Sansui.

For compact discs, Philips has the world's first major production facility--located in West Germany, scheduled to produce approximately 6.5 million this year and capable of expansion to many times its present capacity. In the immediate future, all American companies marketing compact discs--notably CBS, RCA and the Warner Communications group--will be importing them, mostly from the Philips plant in Germany but also in smaller measure from Japan. Production on this continent may begin sometime next year. At least two Washington record outlets, Record & Tape Sales, Ltd. and Serenade Records, already are importing compact discs directly from Europe and Japan and selling them as fast as they come in.

"By the end of 1983," according to Petrone, "world consumption will be around 10 million compact discs per year--and that's just for the first year, the shake-out year. Demand will exceed supply in the United States, unfortunately, for at least the first six months."

FOR ALL his enthusiasm, Petrone concedes that "the consumer will ultimately decide" and that for the immediate future (beginning in 1984) Philips will be simultaneously distributing all its new releases in three formats: compact disc, "black disc" and cassette. But he is instantly off again into enthusiasm: "car models and Walkman-type units are now being developed and are projected for availability by mid-1984."

The current projection is that you will be able to get a car unit for $800 to $1,000; the Walkman model is still a prototype and no unit cost figures have been worked up. But the numbers still raise a nagging question. The price of compact discs and playback units may be remarkably low considering all the new technology they embody. But they are more than most people will pay for a record or for a turntable and cartridge.

Will the people who have flocked to the stores for Walkman-type cassette players priced under $100 also be interested in compact disc units at $800 or more? Early sales figures from Europe (where the compact disc was introduced in March) and Japan (where they have been on the market since October) are impressive. In the first two months in Europe, 50,000 players and 10 times that many discs were sold. For the first six months in Japan, the figures are 100,000 players and 1.3 million discs. Worldwide, the projection for 1984 is 1.5 million players and 25 million discs. But do these figures go much beyond the hard-core audiophile market? When will the prices get down to a mass-market level? Or will the compact disc make everyman an audiophile?

Petrone hopes for mass conversion. "Once you get people accustomed to this quality of sound everywhere--at home, in the car, at a picnic--the demand for it should accelerate," he says. Maybe.

On price reductions, he is vaguely optimistic about the hardware, less so about the software. His job is to sell existing units at existing prices. Loose talk about dramatic price cuts in the near future would not help. Still, he thinks it will happen: "The hardware will come down first, based on the history of the audio business and a situation with 20 or 30 major companies competing for market share. The components of the machine may have a price break in the foreseeable future. But the software still involves a highly technical process of manufacturing. You also have to realize that it's a one-time purchase that will stay with you indefinitely and continue to sound exactly the way it did the first time. You can't buy many things for $20 that can give you that kind of longevity." Perhaps he means that the software price will stay up because, for the immediate future, production of compact discs will be a virtual monopoly.

Meanwhile, Phonogram's black discs will be competing with its compact discs, selling the same music by the same performers for about half the price. Is this any way to run a record company? It will be for quite a while. Nobody expects LP records and tape cassettes to fade away overnight. Petrone's projection is that Phonogram will continue to record music in competing formats for at least seven to 10 years.

The first 100 compact discs from Phonogram will be released officially in August--about 100 titles, approximately two-thirds classical. The figure should be doubled by the end of the year, and next year there should be about 30 new titles each month, including some already familiar in the other formats. Phonogram's ultimate goal is to release its entire catalogue in compact disc form, including many titles not originally recorded digitally. Otherwise, says Petrone, "the shortage of repertoire would be incredible."

Analog recordings reprocessed into digital format should sound better than ever in the final commercial product. That is because very few commercial records capture all of the sound available on the original master tape; there are many steps in processing, and some quality is lost at each step. Digital sound remains unchanged through all processing, at least in theory, because a number is a number--pure signal with none of the noise unavoidable in analog media.

But the question that will be answered (accurately or not) by the general public is whether compact discs sound that much better than the old-fashioned LP or cassettes. A lot of just plain folk will hesitate to say yes because the difference will be minimal on their playback systems. And a lot of golden ears will hesitate to say yes for a variety of esoteric reasons. We're talking here about the kind of people who claim they can hear a difference between transistorized amplifiers and tubes--and who still prefer the tubes. Some of them complain of a weak or lacking sense of ambiance in some digital recordings, attenuation at the high and low extremes of the audio spectrum, or a vague "artificiality" in the sound. They feel that the numbers do not capture all the nuances of the older recording techniques. If they are technically minded, they complain about compromises in the "sampling rate" and other fine digital details.

The simple fact is that digital recording technology on the consumer level is not really as good as it could be; compromises have been made because refusal to compromise would have boosted the cost of development far beyond $400 million. Also because the consumer product is designed to be used in a fairly limited set of circumstances. Compact discs do not actually equal the volume produced by a large orchestra in a concert hall, although they come closer than ever before. "It would be impractical to have anything with a range of 100 decibels," says Petrone, "because who would listen to it, and where?" Pre-digital state-of-the-art recording technology already had outgrown the tolerance levels of the average city apartment--and, for that matter, the human ear.

For the immediate future, the chief limitations of digital recording are likely to be the same as they were for analog recording: the microphones that pick up the music and the loudspeakers that bring it to the consumer, as well as the skill and imagination of the technicians who use the mikes and monitor and mix the sound. Recording is still an art as well as a science, even when it is being done entirely by the numbers.