IN THE entertainment industry, paranoia is part of the air you breathe -- as natural as sand in Saudi Arabia. But the paranoia had a special edge last week in an office high above Fifth Avenue where a grand tradition was dying.

The New York executive offices of Elektra/Asylum-nonesuch Records lie behind a door that is routinely locked, with a glass panel that allows a receptionist to inspect visitors before pushing a button to let them in. Walking over the giver her your name, you notice that she is listening to disco music on a small radio -- and perhaps that is a key to the problem.

In one of the inner offices, Teresa ("Tracy") Sterne, director of Nonesuch Records, is packing to move out. A hand-lettered poster signed by John Cage goes into a box, next to a copy of Sterne's translation of Berlioz's "L'Enfance du Christ," whipped out in a few days during an emergency 10 years ago.

Tacked to a bulletin board over Sterne's desk (one of her two desks with a chair that swivels between them) is a sheet of paper that is now obsolete -- a list of planned recording projects that were quickly scuttled by the company when she was fired. Whether or not the Nonesuch name is maintained (as it will be for at least a while; it is one of the best names in the business), an era is ending -- an era in which Nonesuch established new standards for imaginative programming and strict quality control. The label has become a reflection of the wide-ranging tastes of Tracy Sterne, and that 14-year association has ended -- so suddenly that recording dates were canceled on a few days' notice.

In corporate terms, Nonesuch is the only classical music outlet of the sprawling Warner Communications conglomerate. Historically, it is the offspring of Elektra, a small label founded in 1950 by a 19-year-old named Jac Holzman, specializing in folk music and featuring artists who ranged from Theodore Bikel to Judy Collins. mElektra was born at the precise moment America was ready for its repertoire, and it rode to affluence amid a craze for folk material. In the '60s, it ventured carfully into rock, with such innovative groups as The Incredible String Band and Ars Nova; then in the '70s it was absorbed by Warner Communications, its main offices moved out to California, and gradually it became indistinguishable from other pop labels. Like other pop labels in the year when the boom stopped booming, Elektra experienced financial trouble. And that meant trouble for Nonesuch.

"Classical music is not really in such bad shape," says Joshua Rifkin, who worked at Nonesuch until a few years ago and recorded its best-selling Scott Joplin albums. "It is only a small part of the industry and much more stable in its sales than rock and pop. But it is being pulled under by failures in the rock world."

When Nonesuch was created, it was tailored to the early Elektra clientele -- basically a college audience. The records were inexpensive, the material bright and innovative. It has to be called a "classical" label for want of a better term, but its material stretched the meaning of that fuzzy word to new dimensions.

Piano music, for example. The Nonesuch piano catalogue includes Rifkin's three-record series of Scott Joplin -- a keystone in the revival and re-evaluation of that composer. It has the premiere recording of George Crumb's "Makrokosmos," in which a whole generation's experiments with new ways of producing sound from a piano are integrated into a vast structure that transforms them from interesting noises into musical communication. From Paul Jacobs (who was previously pegged as a specialist in such spiky moderns as Arnold Schoenberg), it offers performances of the Debussy Etudes and Preludes that set a new standard in this music.

This is a small sample from a catalogue of about 300 titles, with special emphasis on contemporary music, pre-Baroque works and neglected popular music from the American past. Nonesuch has specialized in repertory gaps -- music previously unrecorded or not yet done right. Working with a low budget and an active imagination, it is a label for those who are no longer excited by endless reruns of the classical to-40. And in an industry where the top-40 is becoming not the most important thing but the only thing, its days may be numbered.

Keith Holzman speaks hopefully on the phone from Los Angeles. Holzman (a younger brother of founder Jac, who sold the company to Warner Communications in 1973) has been associated with Nonesuch from the beginning in roles that ranged from promotion to production, and now he has been put in charge of the label. "It's a little delicate," he says. "I've been very fond of Tracy, but there has been a feeling for some time that we needed a change of direction. We are hoping that many of the existing Nonesuch artists will remain with the label. I have talked to each of them and asked them to stay with us -- but of course we realize that right now they are caught up in the emotion of the moment and we are not asking for any firm commitment."

New directions with the same artists? When many of them are busy penning protests and some are even talking about the situation onstage at concerts? Where he is not walking on the edge of self-contradiction, Holzman tends to be vague: "There is still plenty of fresh ground to be covered in recording. I am now exploring certain unused categories, as it were -- but this is still in the tentative stage, too early to talk about it."

He is more definite about the immediate future, but it turns out that the January and February releases are all Sterne productions, originally scheduled for November 1979, but delayed by quality-control problems -- one of Sterne's perennial headaches. "I did have complete freedom in choosing artists and repertoire," says Sterne, trying to be nice, " and for that I am grateful."

Several of the musicians who have recorded with her offer a simple explanation for this enlightened policy. "They [the company] didn't know or understand what she was doing," one of them says. "They never knew what they had in Nonesuch, except that the reaction from critics and music-lovers was so positive and it gave them a lot of prestige."

Sterne has a 12-year career as a pianist (beginning as a child prodigy) before going to work for the Hurok organization and then for record companies -- Columbia, Vanguard, and finally Nonesuch, which became very much a reflection of her wide-ranging enthusiasms. "If you look at my experience, I have to be 85 years olde," she says, approximately doubling the actual figure. A few days before her final severance, she was still deeply, intricately involved in the work's details, talking about the rewriting of liner notes, running an appraising eye over the reproduction of a French Impressionist painting for an album cober, listening to a rough cut of a recording of Chinese music that may never see a turntable. The heart of the job she is leaving (and presumably of the many she will be offered) is artistic direction -- working on ideas with artists until they take a form that can be made into a record. It requires a kind of mutual respect and intuitive understanding (as well as musical knowledge, taste and imagination) that are not easy to find.

As for Holzman, the consensus is, as one insider put it, that "he is marching into a meatgrinder." Holzman expects Nonesuch to continue and prosper, and Elektra management says it will keep Nonesuch alive, but some performers associated with Nonesuch are pessimistic. "The label may continue, but as a creative force Nonesuch is finished," said one. Many wonder whether even the name and the older recordings will be around in a few years.

The official grounds for firing Sterne were that Nonesuch is losing money -- $500,000 is the projected loss figure for next year. It seems incredibly high for a company that issued only 18 records this year -- virtually all of them solo piano or chamber music with relatively low costs for performers. But however accurate is may be, it is an insignificant number in an industry where Fleetwood Mac can get $2 million in advance to produce an album and $400,000 was the cost overrun (not the total cost) for an album by the Eagles. Rifkin recalls an album of Renaissance music that he directed when he was a Nonsuch employee. "The performance disappointed me, and it was not released," he recalls. "The cost was between $1,000 and $1,500 and I had to pay it back out of my salary. We had to pay our own way and live very tight, and for a while we had to support the rock operation -- of course, Nonesuch was much more profitable then than it is now."

Exactly how profitable it could be -- in a corporate structure willing to accomodate Teresa Sterne's unique approach to music -- is another question. Answers should begin to emerge when Sterne decides what she will do next. A lot of performing artists and ordinary music-lovers are waiting for that decision.