Gary Karr is the only artist these days who brings out the bulky double bass for concerts. Tonight in the Kennedy Center's Terrace Theater he will play his 1611 Amati.

While talking about his life as a virtuoso performer he is reminded of a story. "In Fort Wayne I was playing with the symphony and this large woman came backstage afterwards and she stood there with her eyes wanting to meet me and she slowly brought her hand up to shake hands, so I grabbed her hand and I said, 'Hi there, how are you?' And she said, 'Wow! I've never met a virtuous before!' "

Ask Karr how much his beautiful, dark-hued monster weighs and he answers, "Lift it! I would guess 30 pounds or so." And what about airplanes and security checks for his friend that travels in a dark blue corduroy cover? "The security infuriates me. They should not be allowed to wear rings. They open up my bass and move their hands all around it. It's got so many scratches on it. It's 371 years old and there've been more scratches put on it by security people than in its entire history. It was built by the Amatis, Hieronymus and Antonius."

Karr, who just turned 40, is not quite as tall as his instrument, which he calls Koussy after its most illustrious previous owner, Serge Koussevitzky, who, before he became celebrated as the great conductor of the Boston Symphony, was the world's foremost soloist on the big bass. Below Karr's trimmed beard and mustache he was sporting a handsome silk tie on which were painted a number of double basses. "I was playing in Ireland and a banker came to the concert wearing it and I said, 'That is ridiculous! How could you be so daring as to wear a tie like that to my concert?' And he said, 'That sounds like a very covetous remark to me,' and took it off and gave it to me."

Is there much vibration involved in playing that bass? "I call it a chocolate feeling. It's a very sensuous, delightful, pungent, strong feeling. Even if you didn't hold it near you, the vibrations are so strong that if you're within one foot of the double bass it makes your whole body rattle."

When did Karr decide he was going to be a virtuoso double bass soloist?

"You know it was Leonard Bernstein -- well it was really Jennie Tourel. The late mezzo-soprano was one of the world's great singers. I was a student at the Aspen Summer Festival. I had been playing the instrument lyrically mainly -- I love to sing on it. Because of that she was attracted to what I was doing. She said, 'You've got to play for Lennie.' So I came to New York, in fact it was 20 years ago that I was on the Young People's Concerts with him. He presented me as soloist with the New York Philharmonic. I think there were 7 million people watching the show."

Tonight Karr will play his own transcription of Aaron Copland's violin sonata. "I went to his house to play for him. After a while he brought out the sonata. After I had worked on it for a while I went back to him with it and we were playing it and in the first movement he stopped me after a couple of pages and said, 'I don't believe it! It's extraordinary. It fits the bass like a glove. I guess back in 1943 when I wrote this sonata I must have had the double bass in the back of my mind.' "

Is anyone writing new music for the double bass these days? Karr, who will return next season as soloist with the National Symphony, said, "I am hoping to interest Rostropovich in a new work being written for me by John Downey of Milwaukee."