Washington music moved from its modest beginnings to the level of mass event in one unforgettable day, Easter 1939. Here, in part, is William Manchester's retelling of that story, from The Glory and the Dream:

"Marian Anderson was (one of the great singers) of the world; 'A voice like yours,' Toscanini had told her, 'comes but once in a century.' But she was also Negro, and when a peppy, redheaded newspaperwoman named Mary Johnson heard of plans for an Anderson concert in Constitution Hall, she played a hunch. Constitution Hall, Miss Johnson knew, belonged to the Daughters of the American Revolution. Calling upon the DAR president, Mrs. Henry M. Robert Jr., she asked her where the Daughters' position was in all of this. Right in the driver's seat, Mrs. Robert snapped, and all the plans could stop right where they were. Neither Marian Anderson nor any other Negro artist would ever be heard in Constitution Hall.

"The next move was made by Walter White of the NAACP. He suggested that one way to draw attention to DAR prejudice would be for Miss Anderson to sing in an open-air, free concert in Washington. She consented, and the feeling in the NAACP was that the Lincoln Memorial would be appropriate. Interior Secretary Harold Ickes (was sympathetic); and the concert could not be staged without the secretary's permission. Told of the DAR's stand, he phoned the White House. The president was about to leave for Warm Springs. Ickes asked him to wait until he could get over there. When Roosevelt heard the details, he ordered Ickes to stage the greatest outdoor concert possible.

"Eleanor Roosevelt resigned from the DAR, and at White's suggestion she and Ickes recruited a blue-ribbon committee of cabinet members, Supreme Court justices, senators, congressmen and other distinguished men and women . . . The audience was 75,000. From the opening bars of 'America' to the last notes of 'Nobody Knows the Trouble I've Seen,' they sat spellbound. Then there was a convulsive rush to the singer, which for a moment or two threatened to become a stampede."

The precedent was set for future ceremonies of moral and political regeneration to be held at the memorial. Starting with this concert--in itself a visionary act reaffirming bedrock American beliefs --the Lincoln Memorial became a symbol of the civil rights and anti-war ideals voiced so eloquently by the man it commemorates.

But it took another 24 years before the stirring words "I have a dream . . ." were voiced by Martin Luther King Jr. from the same steps. It would be another 13 years before the DAR president of 1939 would be proved wrong and a black singer, soprano Dorothy Maynor, would sing from the stage of Constitution Hall, with the National Symphony. Even then, impresario Patrick Hayes recalled, it was "made undervisible" and done through "a quiet arrangement, and a few months later I presented Marian Anderson there," in what is now the Washington Performing Arts Society concert series. LEINSDORF'S REVENGE

The performance of the Boston Symphony's conductor at Constitution Hall on March 17, 1969, was of more than just musical magnitude. Erich Leinsdorf had always been an adventurous programmer. That night, one of his last as Boston Symphony music director, he did the Tchaikovsky Fifth to satisfy the conservatives in the crowd. Then to satisfy himself--and a few others--he played one of the more daring works in the repertory, Edgar Varese's "Deserts," an exercise in brash and sometimes abrasive brass, percussion and electronic tape sonorities. It is music neither alluring nor congenial, but apparently Leinsdorf thought that the sugar- coating courtesy of Tchaikovsky would be balm enough to placate the crowd.

Ha! When the Varese concluded, the booing began in the the boxes at the back of the hall. One man started it and it caught on like brush fire. Then some "bravos" countered and the Boston Symphony conductor bowed in triumph. The audience was beginning to sound as cacophonous as the Varese. Motioning for silence, Leinsdorf declared, "We are delighted to learn that in Washington not only politics is controversial." And with a gleam in his eyes, he turned and conducted "Deserts" again. HARD-SELL CONCERTO

It is a tradition in music for composers to court favor with benefactors by attaching their names to works. What other claim to fame does Kreutzer have besides the violin sonata Beethoven named after him?

It is all perfectly respectable, but at times the gratitude has been expressed a little heavy-handedly. Consider the concerto by Robert Evett performed by the National Symphony in 1963. Evett's work was commissioned by a Waynesboro, Va., firm called Basic-Witz Furniture Industries. Hence the title, the "Basic-Witz" Concerto, a name more memorable than the composition itself.

Symphony manager M. Robert Rogers offered notes in the program: "In honor of the composition and (the company's) 75th birthday, Basic-Witz is introducing a new line of furniture to be called, appropriately enough, 'Concerto' . . . The designer of these new Basic-Witz suites is a Washington resident, Sanford Wallach. Mr. Wallach is represented on our stage at these concerts by the handsome new podium he designed for Howard Mitchell and which has been presented to the National Symphony by Basic-Witz."

Evett's concerto would be recorded by the National Symphony on a grant by Basic-Witz, Rogers added. "The record, which is to be distributed as a gift through furniture stores, will also contain a new proposed official version of 'The Star-Spangled Banner' as arranged for symphony orchestra by Howard Mitchell and the suite from 'The Sleeping Beauty' by Tchaikovsky. Tchaikovsky wrote his ballet in 1889, the year that the Basic-Witz company was formed. How apt that Basic-Witz is famous for its bedroon furniture."

That's packaging, friends. David Oistrakh also played the Brahms Violin Concerto on that program, but it must have seemed an afterthought. THE UNKNOWN PIANIST

One quiet Sunday afternoon in the genteel confines of the Phillips Collection's music room a star was born.

The Phillips has had Sunday recitals for decades, usually featuring young and unfamiliar performers. It is doubtful that many in attendance on Jan. 2, 1955, had heard of the pianist, a Canadian named Glenn Gould.

There is no word in The Post's review the next morning about whether the personal eccentricities at the keyboard--the cut-down piano stool, the heavy overcoat--that later characterized Gould's performances were evident at this his American debut. But his brilliance was; it stunned critic Paul Hume. The Phillips audience heard a typical Gould program of Beethoven, Webern and Bach. Hume's summation: "Glenn Gould is a pianist with rare gifts for the world . . . We know of no other pianist anything like him of any age." TALES OF THE NSO

Recent years have been heady times for the National Symphony.

In his first five years as music director, the magnetic Mstislav Rostropovich has given the orchestra a worldwide public profile that no one earlier would have dared dream for the organization. And in the seven years preceding Rostropovich's arrival, his predecessor, Antal Dorati, made an equally valuable, if quieter, contribution to its development. Dorati interpreted his mandate to be to end the timid programming of the National Symphony's first 40 years. In the 75 programs he conducted, he introduced 64 works new to the orchestra, including 22 world premi,eres and four American premi,eres. One year he conducted a work new to the orchestra every week.

In the earlier years the orchestra's leaders had tended to think small; perhaps in consequence the product was small. Once, in the 1939-1940 season, the National Symphony actually folded. The orchestra needed $115,000, barely lunch money by today's standards, but the board decided that the money was simply not to be had. It cancelled the season and returned the subscription money. Players went unpaid. Soloists were left high and dry. Finally, at the last moment, civic organizations responded and a bit of a season--but not much-- was strung together. The symphony survived.

There is also a rumor, still current, that the orchestra's management of those days muffed a chance to hire the great Serge Koussevitsky. Hans Kindler, the NSO's founding conductor, was retiring and the music directorship was up for grabs. One of those considered as his successor, supposedly, was Koussevitsky, who had just ended 25 historic years with the Boston Symphony and was prepared to come to Washington with his prot,eg,e Leonard Bernstein.

Bernstein, however, said earlier this month that the rumor is unfounded. "It certainly doesn't ring a bell with me," he replied to a query. Kindler's successor was not Koussevitsky but the NSO's principal cellist, Howard Mitchell. TOSCANINI'S TRIUMPH

One key event, on May 25, 1950, persuaded Patrick Hayes that the capital could achieve the musical big time: "It was Toscanini's 1950 concert," he said not long ago.

"It all happened very fast. I got a call just a few months earlier saying that Toscanini, at age 83, had decided to take his NBC Symphony on an exhausting national tour, and I was asked if we were interested . . . He had conducted in Washington only once before, and that was during the war at a Philadelphia Orchestra subscription concert.

"It did raise a few questions. What about the late spring heat in Constitution Hall? Could the maestro take it, or the audience, for that matter? And what could we afford to charge? We finally decided we could charge $7.50 for an orchestra seat and still sell out. That's the same as $40 or $50 now." Four hours after the tickets went on sale they were gone.

"When Toscanini arrived at Union Station, it was like an emperor's train," Hayes recalled. "The concert was extraordinary. President and Mrs. Truman were there. I had never seen anything quite like it. That was when I was finally convinced that the audience for a Kennedy Center and everything else we have now was already here.

All we needed was to grab the opportunity.