When he plays Beethoven's "Moonlight Sonata," as he will tonight at the Kennedy Center in a preconcert recital opening the Mostly Mozart Festival, David Bar-Illan has the fastest hands on three continents.

"It is not true that young pianists today play faster than anyone ever played before," says the 56-year-old Israeli. "We associate profundity with slowness, and it just ain't so.

"Paderewski started that. The 'Moonlight Sonata' became a theme song for him in his later years, and as he grew older, he kept playing it more and more slowly -- mooning over the triplets at the beginning -- and he had a hypnotic influence; all the younger pianists did the same thing. You hear much faster tempos on old recordings. The fastest 'Moonlight' on records is by the late Walter Gieseking, who is not considered a speed demon. Mine is the second-fastest."

Perhaps his speed is a result of the fact that he can get his rest almost anywhere. Though he has homes in New York and Haifa, he jokes that "jet planes" are his only permanent address, and he turns them into a sort of flying bedroom.

"I am fortunately able to sleep on jets," he says. "Whenever I hear the sound of a jet, I fall asleep -- often while it is still on the tarmac. Sometimes I wake up after sleeping for 45 minutes and find the jet still in the same place."

An hour's conversation with Bar-Illan ranges delightfully through an endless variety of topics.

He will joke about Zubin Mehta's two orchestras: "The New York Philharmonic is more Jewish than the Israel Philharmonic."

Or he will talk eloquently about his service with the Israeli Army in the War of Independence: "We had only small arms, rifles and pistols, fighting a mechanized army. There was an embargo on arms to Israel. When they asked Ben-Gurion where we would get our guns, he said, 'From the Arabs,' and that's what we did.

"Whenever there was a lull in the fighting, I would go to practice the piano at the home of a German doctor who lived not far from the front line. I learned Chopin's F-minor Concerto during that war. I was only 17 years old; I left Juilliard to join the Israeli army, served eight months and then went back to Juilliard. Because of my musical talent, they didn't ask me to serve the normal three years."

Bar-Illan and his wife Beverly have five children ("his and hers," he says). One son (his) "has degrees in political science and French from Columbia, so he has decided to be a rock star. He seems to have talent; I wouldn't know. Those who know tell me he has talent. He loves classical music and uses classical themes in his songs, but I can't recognize them."

On his personal habits, which seem rather colorless compared with his quick, agile mind: "Some of my colleagues practice only two hours a day; I have to do six. I try to use the rest of my time profitably and economically; I don't play tennis or chess; I don't go to the beach; I don't go skiing. Mine is a sedentary life, so I do calisthenics every day."

What are his hobbies? Writing articles for the Jonathan Institute, an antiterrorist organization, of which he is a founder.

"It was founded 10 years ago after the raid on Entebbe and named after Jonathan Netanyahu, who was the commander of the rescue mission and the only Israeli soldier who died in the mission. It was an absurd death; he was killed by a sniper when the fighting was almost finished."

Bar-Illan works for the institute, he says, because "everyone has some kind of responsibility to his time as well as his art."

He says the institute exists to express opinions on terrorism and hopes "to change government policies in the right direction."

Some of his articles -- for example, one that appeared recently in The Wall Street Journal -- imply that terrorists are working for the benefit of the Soviet Union. His own policy toward the Soviet Union is hard-line, and he has come prepared with a tidy little oral essay on "the fraud that passes under the name of 'cultural exchange':

"It's like motherhood, you can't talk against it, and it's wonderful to get to know one another's artists. But the Soviets determine not only which of their artists can come here but which of ours can go there," he says. "They decide who is kosher, if I may use that expression, and apparently nobody associated with Israel is kosher.

"Why have there been no invitations to Mehta, Stern, Perlman, Zukerman, Barenboim? These are not exactly unknown musicians. With such control, it ceases to be cultural; it is political. And it ceases to be an exchange; we are letting them make the decisions. By allowing this, we tell the Russians, 'No matter what you do, we are so eager for friendship that we will accept it.' "