We meet pianist Claudio Arrau in the gloomy lobby of the Ambassador East an hour before his matinee. A snowy Friday.

Plaintive, he confides that the hotels restaurants and room services were closed the day before, Thanksgiving, and he had to eat at a neon-and-stainless-steel place called Mitchell's. He never eats before a concert. He is hungry.

We climb into the orchestra's rented limo. He's aglow over the ballet film "The Turning Point", ("the most wonderful experience!") and the Wednesday night concert ("the orchestra played like angels!") his first time with the Chicago Symphony in six years.

"They tried to cancel New Haven," says Friede F. Rothe, his personal manager, protector and friend for 30 years. "They forgot about Thanksgiving. Usually he gets a free day between. He had 20 invitations to Thanksgiving dinner here but turned them all down and spent the day in his room, reading."

After Tuesday concert in New Haven he got to bed at 1 a.m., slept till 6, met the limo at 8, flew into Chicago at 11, and by 1:30 was rehearsing with the symphony for a concert that night.

Through next March he will do 48 concerts in 26 cities, Toronto to Palm Beach, Los Angeles to Washington, where he opens Tuesday night with the National Symphony under James DePreist. Then 10 days of rest. Then off to Europe for recitals through June.

Then Australia in '79 and maybe Mexico, and Japan in '80. He used to do 150 concerts a year. He's down to 100 now. Next Feb. 6 he will be 75 years old.

"We thought he'd be free this summer," Rothe says as the limo nudges through the holiday shopping traffic.

"Usually he teaches in the summer, and last summer he finished editing all the Beethoven sonatas after eight years.But then Schirmer's asked for a new edition of the five Beethoven concertos. So he'll be doing that all summer. And then the road again."

He loves it. A tourist. Visits museums, goes to plays, roams the cities of the world. He also loves to sit in his room and read. Two, three hours a day, at least. "How cay you keep up with the world with less?" Adam Smith's "Powers of Mind." Rereading "Crime and Punishment." "It shocked me, this time. That world of crazy people. For the first time I felt it was a little farfetched Marquez Fuentes. Jung. Anything he can get his hands on like a man marooned.

Sometimes his wife of nearly 40 years comes with him. A former singer herself, German they met in 1935 in Germany: he promised to call her: she waited three months: later learned he had been playing entire keyboard works of Bach in 12 sensational recitals, now three children, six granchildren. None of them has anything to do with music.

"It's hard on his wife," Rothe says. "After a concert he has to unwind, it takes hours, he may stay awake to 3 a.m. But he constantly renews himself. He'll put two chairs together facing and sit there with his feet up and his head resting very carefully - he keeps his hair slicked down because he can't stand musicians who affect those dramatic manes of hair all wild and he goes off to sleep just like that for a half-hour, an hour."

Between dates he goes home to Long Island, but still there are times when he must carry clothes for two climates. Leave Berkeley Jan. 17, arrice Cincinati Jan. 19. Luggage: three dress suits, three pair shoes, black velvet cape to absorb the sweat after a concert. A dozen jars of pills. Rosehips. The battered satchel containing his personal scores, never checked, never out of his sight.

Six weeks in summer he goes to the Vermont place to meditate and practice and garden and contemplate his Tang porcelains and pre-Columbian art and work on the Beethoven edition and receive pilgrims who want him to listen to them play.

There is so much to do. He no longer plays Bach because he feels it should be done on a harpsichord, so he is thinking of taking on the harpsichord. For a time he was in Jungian analysis, is still fascinated with Jung's ideas.

His great cause is Amnesty International, the worldwide crusade against torture and police brutality, which he more or less rescued, just before it won the Nobel Prize, with his benefit recorded concert that brought in $190,000. Since the fall of Allende in 1973 he has refused to play in Chile, his native land. Hasn't appeared in South Africa for nearly 20 years.

Now he's talking about food again. "Mitchell's wasn't so bad. A beautiful girl served my dinner, so it was a pleasure. I love all the fattening things in the world. Sunday I will fast."

"He's on a permanent diet," Rothe says proudly. He doesn't drink or smoke, used to take a little wine, but now not even that.

Outside Orchestra Hall a burly man detaches himself from the wall, lunges for the pianist's hand, gushes. It is Rothe who winces at the handshake.

(Both have families of their own, but they act like an old married couple. Later, when the concert is over, they will chatter about where to eat - she doesn't want him to venture out into the blizzard: he hates the room service food, she slyly reads him the room service menu; he sulks. And when they do finally wind up at Mitchell's again: Doesn't he want a baked potato? No. But just a piece of one, to keep up this strength? No, he wants a salad. They are no quarreling. It is how they get along after 30 years together. It's rather endearing.

Belowstage in the dressing room he gets out his music, sits down with a cup of coffee from the pot which has been perking there for him. We step outside.

"He's going into his shell now," she says. "He'll go over the score note by note for half an hour".

It is the Beethoven 5th Concerto, the Emperor. Gradually, backstage noises increase. Bassoons. Violins. Trills. Arpeggios. Noodling. Inside, via the mirror, we can see Arrau, profoundly concentrated. His hand moves. He nods once with decision.

The warning buzzer. Giulini drops in, they talk in German, one of Arrau's five languages. Smiles. A pat on the back. A light handshake. Giulini, lean and graying, towers over the 5 feet 6 Arrau. He leaves.

"He's got a new superstition," Arrau chuckles as he comes out into the cluttered corridor among the trunks and wardrobes. "He won't take the elevator up to the stage."

Musicians hurry by with their instruments. The air vibrates. Rothe steps up to him, holds his hands, bow to kiss them revently, murmurs. He is not looking at anything. An inward stare. He takes a deep breath.

Backstage: falts, ropes, bulletin boards. On a desk, Arrau's bottle of Evian water, Giulini comes up the iron stairs, greet techinicians. Then Arrau steps off the sentry-box elevator with its tiny square of red carpet. Technicians bow them through quickly, open door to stage rear. Out they go. Brisk. Into the applause-storm.

At the piano, Arrau fixes attention on the conductor. All the rushing is done now. The chatter and the faces and the knot in the stomach. All done now. The silence gathers.

He was 4 years old, so young he can't really remembered just when he first took to the piano, but he does remember having his dinner actually spooned into his mouth while he played on, and he knows that he taught himself to read a Beethoven sonata off the printed page before he could read words, and later his mother, a fine pianist herself, prepared him for his first concert, in Santiago, at 5.

You think about that as you watch him play, you think about that 4-year-old with his feet not halfway to the pedals, that little kid out there playing Chopin on the stage at 5 - 5 - and your mind ticks off the milestones of his life: sent to Germany at 7 by the Chilean government to study with Martin Krause, (a pupil of Liszt, who was a pupil of Cerny, who was a pupil of Beethoven), the Liszt Prize at 16 and again at 17 - it hadn't been awarded for 45 years; gigantic projects, playing all the keyboard works of Mozart, Schubert, Weber, the sonatas and concerti of Beethoven; a half-century of touring the world; the international prizes, the endless roster of recordings, the volumes of editings - But you keep coming back to the memory of that child as you watch the veteran looking up raptly at the conductor, bending over the keys, lost in a world of his own making.

When he was 15 and Krause died, he was shattered, for he sensed that he would have to re-invent himself, would have to outgrow the prodigy who played by intuition, so he stopped for a year or two, relearning, maturing, determined to be taken seriously as an artist, finally celebrating his arrival with a brilliant explosion of music: the Liszt Prizes and in the same year his London debut when he played Bach's Goldberg Variations and four Scarlatti sonatas, a stupendous outpouring.

Famous for his immense repertoire, still recording constantly, he does tend now to stick to a few reliable warhorses when on the road. He plays from the shoulder, not in the Russian style with the elbows close, but getting his whole back into it. Here and there he misses a note, but what you notice are the coherent dynamics, the crisp attacks, solid, never flamboyant, the timing and most of all the intelligence of his playing: the mind always at work.

(He feels Chopin has been abused, treated as a salon composer, and his Chopin is not the one we expect: There is iron in it, the dark Chopin, the exile, the dying.)

It is a new piano, the action is a little heavy. There is a man in the front row who can't keep still, acrosses legs, digs in pockets, yawns. . . Giulini is taking it a trifle slow. . . But Arrau isn't woolgathering: at every entrance he is right - there, competent, sure.

When he no longer finds new ideas and meanings in a work, he simply drops it, leaves it behind, gutted, while he goes on with the search across that peculiar rectangular landscape which dominates his life, for though he only practices two or three hours a day now and not the 10, 12, 14 hours he used to do, there is always a piano in his hotel room, always a piano a few steps away, an extension of his body, his brother, his fate, this long, shiny, black wooden thing with the grin of white ivory teeth that has been confronting him since before he can remember, since some lost afternoon when he first wandered over to it, magnetized, and reached up to his chin level and poked at a key with a curious finger and heared that sound -