Larry Christiansen sits, comfortably but tensely, on a sofa, his eyes fixed on Wisconsin Avenue outside the window, his back turned to a roomful of people who are sitting, staring at chessboards, or walking around quietly, talking in whispers.

Although he seems to be doing nothing much, occassionally sipping a cup of coffee from an urn near his right hand or crushing out a cigarette in the ashtray at his left, Christiansen is hard at work. The tall, slim 23-year-old from Modesto, Calif., is a grandmaster, a member of the international elite of chess, and while his eyes wander down the street he is really looking at pictures in his mind. He is playing 10 games of chess simultaneously without looking at his opponents or a board.

The scene is the Martens Volvo showroom in Northwest Washington, on Sunday, and a Volvo stands between Christiansen and his 10 opponents, blocking the view. The opponents are seated at tables around three sides of a hollow square, and a young player, Vince Moore, walks around the inside, making Christiansen's moves on the boards and calling out the opponents' moves to the grandmaster

"On board one, king takes on h7," says Moore, and after a few seconds a reply comes back from the unseen Christiansen: "Knight takes on d5." Once he begins: "Rook takes pawn," and his opponent's eyes light up, but he corrects himself immediately: "No, bishop takes pawn," and the opponent's expression becomes thoughtful again. A trap has been avoided.

The pace of the games is fast. In the first hour, Christiansen has made 15 moves each in 10 games -- an average of one move every 24 seconds. His opponents have 10 times as long to look at the board and think -- about four minutes per move.

There are only three other masters in the world who now play more than four games of what is called "blindfold" chess (although no blindfold is used) simultneously, though this form of the game was invented in the year 970 by a Greek player named Tchelebi, who played only one game at a time. Louis Paulsen, an American player, raised the world record to 10 games in 1857. The current record is 34 games, held by George Koltanowski, Christiansen's teacher, who thinks Christiansen will eventually break that record.

Christiansen's opponents are a cross-section of chess in Washington strong club and tournament players like Homer Jones and Leif Karell on boards 1 and 2; young whiz Bill Mason on board 4, who has nearly reached the expert rating at age 16 and will probably be a master in a few years; average players like Clarence Beverly on board 8 -- holding his own until late in the game, deep in study most of the time but once in a while getting up to stroll around and look at the other boards. "I think I'm doing fine for a nobody," he says, about halfway through, but he is being pushed back slowly and can expect a hard-fought loss.

One opponent is a small, specialized computer, a Chess Challenger, supplied by a specialty shop called The Math Box. Another is a titleholder, Dr. James Slagle, blind champion of the U.S., who will be playing in the blind chess Olympics in Holland this summer. Slagle examines his position on a special board with the black squares raised and a special pin in the black pieces to identify their color.

In the second hour, as the games get more complicated, the pace slows and Christiansen is taking an average of 36 seconds per move. Fatigue is beginning to show a little in his hesitations, and occassionally when he announces a move Moore replies "That's illegal" or "You can't do that." "Oh, yeah," says Christiansen and announces a correct move. Later, he explains, it's not that he forgets the positions but he mixes up one board with another. "I remember the games for a while after they're finished," he says, "but I try to forget them as soon as I can."

Playing 10 games of blindfold chess simultaneously, Christiiansen does not function at his grandmaster level, as he will when he plays in the U.S. Championship later this year. He expects to lose a few games, and he does -- first to Karell and later to Slagle. Three games are drawn, including a grueling one that goes more than 70 moves.

The computer is the first opponent to lose; it blunders away a knight, and then Christiansen announces a checkmate in four moves. Soon afterward, some of the human opponents begin to crumble, and some of them join the small knot of spectators following Moore from board to board, watching the action.

When the final game ends in a draw, the audience -- including opponents -- breaks into applause, and Christiansen comes out from behind the Volvo to give prizes to the Winners. "Draws only get a pat on the back, sorry," he says, signing vouchers that will secure the winners their prize -- "One Regular Family Order" at Church's Fried Chicken, a national food chain that is sponsoring Christiansen's tour from Canada to Florida as part of an effort to promote chess -- and fried chicken.

So far this year, Christiansen has played about 180 blindfold games, 10 at a time, and four or five times that number, 25 at a time, while looking at the boards. Does he think it helps or hurts his tournament play?, he is asked after the four-hour match.

"It probably hurts a little," he says. "It takes a while to recover from something like this -- but it helps me to earn my living as a professional chessplayer." For better and/or for worse, he will be doing it again tomorrow in Providence, R.I.