There is something new in the May issue of the Schwann Compact Disc Catalog: a full page (Page 29) listing the first 52 digital audio tape (DAT) recordings available on the American market. Music lovers eager to sample the latest state-of-the-art technology in sound reproduction can choose between Bach's "Brandenburg" Concertos; five collections of baroque trumpet music; Chick Corea's "Light Years"; and the Glenn Miller Orchestra playing "In the Digital Mood."

The only problem (a temporary one) is finding something on which to play this music.Some audiophiles in the northern states have been slipping across the border and coming back with DAT machines, which are available in Canada. In fact, these machines, introduced in Japan a year ago and in Europe six months ago, can be bought almost anywhere in the civilized world except the United States. That situation will probably end Wednesday, when at least one company (Marantz) and probably several others are scheduled to import the first machines to be regularly marketed in this country. On the same day, the Recording Industry Association of America (RIAA) will slap one or more lawsuits on the offending companies. Having failed to stop DAT in Congress, the record industry is now prepared to try the courts.

The most important thing about digital audio tape, like any form of digital recording, is what you don't hear. Digital sound recording is a medium (the first in history) that leaves no perceptible trace of itself - puts nothing between you and the music.

Next in importance, for the immediate future, are the reasons why we haven't been hearing DAT in the United States. The short answer is that it would remove state-of-the-art musical reproduction from total control of the recording industry.

DAT is the tape equivalent of the compact disc, the medium that has risen to dominate the recording industry in the last few years. DAT recorders look pretty much like the analog cassette recorders that have long been familiar. Their range of sizes is almost the same, down to the size of a substantial hard-cover book, and they are equipped with the same sorts of buttons and functions. They take a cassette that is about 1 1/3 by 2 7/8 inches - smaller than standard audio cassettes but bigger than microcassettes often used for dictation. The DAT cassette is shaped like a small video cassette, with a hinged front that drops down to protect the tape when not in use. The cassette cannot be spliced because there are consecutive location codes printed on it to allow the DAT player to find a precise spot on the tape - a significant advance over the old turn-counters on analog tape decks.

The DAT machine can be plugged into existing jacks on any standard audio receiver or preamplifier and operated essentially like any other tape recorder. Though some audiophiles eventually may want more powerful amplifiers and/or speakers to accommodate the medium's wider dynamic range, DAT, unlike the quadraphonic systems developed and abandoned in the 1970s, will not threaten the other components in your system - particularly CD players - with instant obsolescence. It will merely complement them.

The CD, in fact, has been much more disruptive. Though the mopping up process will take time, the CD for all practical purposes has already killed the LP. DAT is not likely to kill CD in the immediate future. There is room for coexisting tape and disc technologies, which have enough different features and advantages to make them essentially noncompetitive.

Tape, which does not require the kind of precise tracking needed to scan a disc, will probably remain the preferred medium for car systems, Walkmen and other uses where portability is desired. There are portable CD systems, but their operation is not as trouble-free and shock-resistant as tape.

On the other hand, disc technology offers instant access to any part of the flat surface on which the material is stored, whereas even with digital tape, you still have to fast-wind through items A, B and C before you can play D. In a nutshell, the disc medium is best for a collection of short items from which you may want to play one or two; tape (which has a much longer potential playing time than disc) is best for long works - operas or oratorios - or assemblages of shorter works that you may want to play frequently in a fixed order. Because of these differences, DAT may take a substantial share of the audiophile market (as analog cassettes have done with LPs), but it is not likely to eliminate CD.

The biggest difference between CD and DAT right now is that DAT is a medium for recording and playback, while CD is playback-only. If a system is ever perfected for home-recording on CD, the competition between the two will become much more significant and disc recording would have some strong competitive advantages. Research is underway, and Radio Shack has already announced plans to market a recordable CD of some sort this year.

On grounds of pure sonic superiority, DAT will certainly undermine the market for analog cassette tapes and recorders, but probably won't eliminate them in the near future. One key factor is price. It is expected that a blank DAT cassette with two hours' playing time will cost about $10, approximately twice the cost of a top-quality analog cassette. As long as the tapes and hardware for analog recording remain significantly cheaper than DAT, there should ba a market for music in the analog tape format. That market could disappear if DAT prices drop enough. But DAT is unlikely to ever become cheap enough to wipe out analog cassettes in the vast market where relatively low fidelity will do.

The chief physical difference between DAT and other tape recorders is one you cannot see unless you take the machine apart; its record and playback heads do not stand still while the tape passes by, as the heads do in an analog recorder. DAT heads, which either set down or pick up the magnetic signal on the tape, move across the tape like the heads on a videocassette recorder. When they go on sale in the United States, early models are expected to retail for $1,500 to $2,000. If they follow the trend of other electronic equipment from computers to CD players, the prices will go down fairly soon and the quality may go up.

While the DAT recorder does not look like a menace to our musical culture, the recording industry has pushed all its panic buttons to stop it. There has been intensive legislative lobbying, an enourmous public relations campaign, technological proposals that would amount to mutilation of DAT hardware and threats of lawsuits against any company that imports DAT equipment for the consumer market.

If this opposition has not stopped DAT, it has certainly slowed it down here, compared wtih Europe and Japan. And the RIAA, despite lost battles, is not abandoning the war. "it is our intent to sue," threatens Jay Berman, president of the Recording Industry Association of America. He charges that DAT recorders will be used to "rob the American music community of the right to be paid for the music we create."

This attitude contrasts sharply with the industry's reaction to the arrival of the compact disc five years ago. CDs were welcomed enthusiastically by American recording companies and have given the industry a financial shot in the arm. The dollar volume of production and shipments in all forms of recording (as measured in list prices) rose 20 percent last year, from $4.65 billion to $5.57 billion. And the fastest-rising part of the industry was the compact disc, up 93 percent over 1986 from 53 million units to 102.1 million. These CDs had a list price value of $1.6 billion. LP sales peaked in 1980 and have been declining ever since - 15 percent last year, when the list price value of LPs distributed was only $793 million, half of that for CDs.

But audio tape is still the backbone of the recording industry and still growing. Last year, 410 million professionally made cassettes were distributed in America, 19 percent more than in 1986 and four times the number of CDs. So the industry has nothing against digital recording per se or audio tape per se. Why the problem with DAT?

The problem with DAT, in a nutshell, is that it's too good. Some of its more enthusiastic fans claim that DAT sound is actually better than CD sound. It might be prudent to wait a while before jumping on that bandwagon, but DAT sound is likely to be exactly as good as CD sound, and that's too good for the RIAA. In Congress, in the courts and in the media, industry spokesmen have complained that DAT makes it possible to produce copies of commercial recordings that are indistinguishable from the originals. Copying at that level of quality "could be devastating to our already battered industry," says country singer Barbara Mandrell in a statement solicited by the battered $5.57 billion industry with production up 20 percent in the last year.

Home copying has been a significant activity since at least the mid-'70s, when analog audio cassettes (aided by the Dolby process for noise reduction) reached a level of sound quality satisfactory to most music lovers. And the RIAA has fought against analog cassettes, but not with the ferocity it has mustered against DAT. Part of the problem was that the audio cassette sneaked up on the industry. It began as a sort of toy - something for dictating letters and preserving baby's first words. Then the sound began to be refined, improved tape formulas were developed, noise was reduced, dynamic range expanded, and the industry was faced with an almost foolproof, high-fidelity home system that made every man his own recording company.

The proliferation of the analog cassette has undeniably led to a lot of record copying, and that may have had something to do with a temporary slump in record companies' revenues in the late 1970s. But since 1979 the growth of prerecorded-cassette production (from $82.8 million to $410 million) has sparked the growth of the entire industry (from $3,68 billion to $5.57 billion).

The fairly satisfactory sound of homemade analog cassette recordings, when done with care on good equipment, has become better than ever. When copied from CDs, they are usually superior to most predigital commercial recordings on either LP or tape. The analog cassette sound may compare unfavorably with the crisp, clean, dynamically wide-ranging sound of the original compact disc, but the differences are hardly noticeable when heard on the kind of equipment available in most American homes. Still, the industry apparently feels it's too late to declare war against the analog cassette. Or perhaps it fears it could not win that war.

The DAT menace, however, is strong enough to rally the RIAA for a last-ditch battle. The superiority of DAT recording becomes crucial when one begins to make copies of copies of copies. In analog recordings, the quality of the music would decline each time it passed into a new generation fo copies. Not only would the noise-to-signal ratio increase as the background hiss and other types of residual noise accumulated; various kinds of distortion, tolerable in the iarlier generations would compound themselves to a level where the music could no longer be recognized. making 10 generations of an analog recording is something like typing a telephone number, making a photocopy of it, then copying that photocopy, hten copying a copy of the copy for 10 generations. Try it and see how long the number remains legible.

Digital recording, on the other hand, is like typing the number over again the same way 10 times. With DAT, ideally, all noise and distortions would be eliminated. The system records sound as a stream of numbers (digits) rather than the physical wave forms fixed in vinyl or the magnetic patterns imprinted on a ribbon of iron oxide that constitute anaolg tape recording. The 10th-generation copy would be identical with the original. The potential for copying material through endless generations may worry the RIAA more than the prospect of one person making and selling multiple copies in a single generation. That is known as piracy, and it is already quite properly, outlawed.

Ultimately, the reason for the industry's opposition to DAT boils down to dollars and cents. In popular music particularly, record companies usually enjoy a monopoly on a particular item - unlike in classical music, where most of the blockbusters have long been in the public domain. This monopoly position allows a level of price fixing that is undermined when the product can be easily duplicated. The ability to make your own recordings at home does not absolutely destroy the value of the professional product, but it introduces a competitive factor.

In practical terms, DAT will make it hard for the record industry to price its products much higher than the combined costs of the tape, your labor and the depreciation of your recording equipment. In other words, what DAT means in the long run is that the cost of CDs will have to come down below $10 to be competitive. That has already begun happening in classical music, which has a built-in competitive element. It is now possible to buy a complete set of Beethoven's nine symphonies, on five CDs, for under $20. And MCA has introduced a "Double Decker" line of classical CDs that will be sold in pairs for the price of a single midline CD (usually $8-$10.) The pressure of DAT is likely eventually to force prices down similarly in the pop field.

So the RIAA has already tried to legislate the implanting of a "copycode chip" in all DAT equipment sold in the United States. The chip would prevent the copying of CDs on DAT, and it was seriously considered by Congress until the National Bureau of Standards criticized it on two grounds: It would degrade the signal put out by the DAT, and people with electronics skills could easily find ways to bypass it.

Lawsuits to prevent private copying of recorded material have already been fought all the way to the Supreme Court, and the right of Americans to tape proprietary material for personal, noncommercial use has been upheld. The recording devices primarily involved were VCRs, but the legal principle remains the same. This does not mean that the recording industry will not try again what has already been tried by the movie industry, but it does mean that chances of success seem slim. When the dust settles, there will still be the problem of arranging for equitable payments to artists whose material is being copied. But it doesn't look as though that can be done through attacks on the copying hardware.