Twenty years ago, a young American pianist named Van Cliburn swept Moscow's awesomely regarded Tchaikovsky Competition and, photographed in the embrace of Premier Nikita Khrushchev, made front pages around the world.

When RCA recorded Cliburn's winning interpretation of the Tchaikovsky First Concerto, it became the first and only classical LP to lead Bill-board's Top 100, and the most successful classical record ever made.

"Everyone got lucky then, with the ticker tape parades," says a company official now. "It was as much a political event as a musical event."

RCA thinks it has gotten lucky again.

This time it is because of President Carter's invitation to Vladimir Horowitz, who is 73, to play a recital at the White House tomorrow that will be seen nationally that night on public television.

The event, with its attending publicity, is being seen as a golden opportunity to maximize sales on Horowitz's latest RCA recording - which a company official describes as "the most exciting classical prospect we've had since the Cliburn."

So by Monday, 50,000 recordings of Horowitz's Jan. 8 Carnegie Hall performance of the Rachmanknoff Third Concerto will begin arriving at record shops around the country. That's the largest classical pre-order since Cliburn's, 20 years ago. The discs will be mailed today from the RCA factory in Indianapolis.

Company officials stop short of saying that the timing of the release is entirely the result of the White House invitation, but they acknowledge that they knew about the Carter's plans before they set the date.

"Admittedly this is not quite the extent to which we blitz the market with the latest Bowie," said Glen Smith, director of RCA's Red Seal merchandising. "But in classical music Horowitz is today's ultimate superstar. It would take the return of Caruso doing complete operates to get much bigger than Horowitz. He far outsells many of our pop stars."

Horowitz's concert appearances have been rare in recent years, and the Jan. 8 performance, with the New York Philharmonic under Eugene Ormandy, was the first time in 25 years he had played with an orchestra, and come 50 years after his American debut.

These days record companies normally depend on the envormous youth-oriented pop market for their big profits, and classical disc normally are launched slowly. The idea is that pop discs make their biggest profits in the short run.

"A Fleetwood Mac record might be selling millions one year, and be practically dead two years later," said an RCA spokesman.

By comparison, profits from classical records are made in the long haul. It was 5 years after its release before Cliburn's Tchaikovsky became the first classical LP to sell more than a million copies. About 17 percent of RCA's present sales are classical, a large percentage for a major company.

With the Horowitz disc, the object is not to break Cliburn's record, as it were. "This is certainly the most exciting classical prospect we've had since then," said Smith. "But nothing will ever outsell the Cliburn. I would hope, though, that with the Horowitz we would be well into the six figures before the end of the decade."

Getting a record into the shops in two months is a breakneck procedure, complicated in this case by severe weather in Indianapolis and power shortages because of the coal strike.

But the biggest problem was polishing the record to Horowitz's perfectionist standards. "It was recorded before the live audience on Sunday, Jan. 8. Then on Wednesday we had another session there to clean up some minor blemishes," according RCA producer Jack Feiffer. "Basically we just fixed some balances and replaced a spot where there was distortion from FM interference."

By the second week in February the fully processed test disc was completed, but Horowitz was in Los Angeles, repeating the Rachmaninoff Concerto there. "He was staying in a hotel so we had to play it one night at the apartment of a friend of mine who is a movie sound technician," Feiffer recalls, "and Horowitz was so impressed that he began to fear that the Rachmaninoff would overshadow his recently released recording of the Liszt Sonata, which he regards as his favorite anniversary release because the Sonata was on his debut recital program."

Feiffer suggested a publicity appearance to promote the Liszt record, "something like an autograph party at a record store," and to his surprise Horowitz agreed. It was something the normally reclusive pianist had done only twice before in his career.

Thus, after advance publicity, on Valentine's Day Horowitz appeared at 4 p.m. at the Tower Record shop, a building with only about 6,000 square feet of floor space in Westwood Village, a shopping center near Beverly Hills.

A line had been forming since noon and the number of persons who came wa s in excess of 3,000. Scheduled to leave at 6, Horowitz decided to stay until he greeted everyone. In 4 1/2 hours he autographed 1,800 records and signed 1,200 gift certificates for the Rachmaninoff. Meanwhile, Mrs. Horowitz, daughter of the late Arturo Toscanini, was autographing records by her father.

"At one point, we ran so slow on records," recalls karen Crumley, the shop manager, "that we had to send halfway across town and buy out the warehouse on Horowitz records."

Apparently it was the Carters who suggested a White House concert, after reading about the Carnegie Hall performance in January.

The White House program will be predominately-Chopin, given before 250 invited guests in the East Room. It will be broadcast live at 4 p.m. on National Public Radio (WETA and WAMU here). The television program begins at 10 p.m. RCA will record the event which is Horowitz's second White House concert. His first was during the Hoover administration.

The pianist returns to Washington for a public recital in Constitution Hall on April 2.