Pianist Ken Noda, who is all of 20, made his White House debut yesterday afternoon in the East Room, under the patronage and in the presence of the President and Mrs. Reagan.

It was this year's opening concert of the excellent "In Performance at the White House" series, in which established performers introduce major young performers who are on the way up.

Last year the emcee was Beverly Sills, and this season it is Itzhak Perlman. Nancy Reagan hosts the series. This concert will be broadcast Wednesday on Channel 26 at 8 p.m., through the Public Broadcasting Service, which, the president noted in his remarks yesterday, is now in its 30th year.

After the concert, Reagan was full of praise for Perlman and Noda.

As one of their encores, they had just played a perfectly gorgeous transcription for violin and piano of Chopin's C-sharp minor nocturne. As Perlman explained to the invited audience of about 100, one drawback of being a violinist instead of a pianist is that "we can only be jealous of them, because they have their Chopin."

In the accolade that followed, the president focused on the pluses of being a violinist, at least one like Perlman. It demands, he observed, "the nerves of a bullfighter, the concentration of a Buddhist monk, and" -- he added after a carefully calculated pause -- "the ebullience of a newly elected congressman." The president also noted with delight that Perlman's apartment in New York once belonged to Babe Ruth, but he drew no conclusions from that.

Reagan told a famous story about the late pianist Artur Schnabel. Schnabel was asked the secret of his music-making, and he replied, "Well, I always sit down at the keyboard. And I always make sure the lid is open," Reagan related, to much laughter.

The president then payed tribute to Noda's "great talent" and said he was so impressed that "if you want to join the Marine Band, I'll sign you right on."

After the recital the Reagans greeted their guests in a receiving line and retired to the family quarters.

During the reception that followed in the State Dining Room, Noda said the opportunity to make a televised White House debut came like a bolt out of the blue. "I just got a call from Mr. Perlman one day in September, and he asked, 'How would you like to do a recital with me?' I said I would like to, and then he added 'How would you like it to be at the White House?' and I was left sort of speechless."

The performance was superb. Perlman and Noda collaborated on Stravinsky's Suite Italienne.Boda then played the great Mozart D minor Fantasia, followed by a thundering rendition of Chopin's G minor Ballade. There followed the Chopin Nocturne with Perlman, and a violin-piano transcription of a dance from de Falla's opera, "La Vida Breve."

At the reception, Perlman said that Noda, who is already building a reputation as one of the finest of American classical musicians, was the only person he considered for yesterday's presentation. "My wife and I were talking about it," he recalled, "and we both thought of Ken, and I said 'God, that's it.' "