"Coming down to Washington doesn't seem like playing on tour," says Peter Oundjian. "It's our home away from home."

Oundjian is the first violinist (and only non-Japanese member) of the Tokyo String Quartet, which has its headquarters in New York and spends more time in Washington than in Tokyo. The Tokyo Quartet visits here for several days at least three times a year; tonight, at the Corcoran Gallery, it will give the last of the three concerts it plays there each season.

Elsewhere, the Tokyo plays to put bread on the table; in Washington, it plays to pay the rent -- not on the members' homes but on their four instruments. Made by Niccolo Amati in the third quarter of the 17th century, the two violins, viola and cello that the Tokyo Quartet uses in 100 concerts around the world each season are the property of the Corcoran Gallery, which loans them to the quartet in exchange for unpaid performances in the gallery's intimate Hammer auditorium.

Actually, it's slightly more complicated than that, as Oundjian explains: "The Corcoran is not allowed to lend anything directly to an individual; it has to go through an institution. In this case, the institution is American University; they borrow the instruments from the Corcoran to lend them to us, and they cover the insurance costs for us. So we play three concerts at the Corcoran in gratitude for having the instruments, and we play two concerts and give two master classes or composers' reading sessions at American University in return for their help. It's a very nice arrangement for everybody, and we have a little home in Washington."

It is even a nice arrangement for the instruments, which are kept creatively busy rather than languishing untouched in glass cases. The folklore of musical instruments (with growing support from expert observers) holds that stringed instruments deteriorate if they are not played regularly. Exposure to the vibrations produced in making music helps to keep the wood in a violin "alive" -- resonant and responsive -- an effect something like that of regular exercise on a human body. "There are are some very sad stories about instruments that were not played and were left in the wrong place," Oundjian says. "Sarasate's Strad was destroyed by being left unplayed and exposed to sunlight."

When they talk about their instruments, the members of the quartet might almost be talking about human colleagues; each of the instruments has a personality of its own, and there has been one intrument-swap among the quartet's members to enhance compatibility. Second violinist Kikuei Ikeda almost sounds like a lover when the subject turns to his violin, which was not his when the quartet began using these instruments.

"That violin is like a jewel," says Oundjian, who began as its proprietor but later felt that he had to give it up. "In fact, it is a jewel; it is inlaid with rubies and emeralds in a fleur-de-lis pattern -- very delicate. It is the only Amati inlaid violin in existence; it was made in 1656 and was dedicated to King Louis XIV, which also gives it historic interest. It was originally played by our first violinist, but I found it a little difficult to play, and I've always loved Kikuei's violin -- it's so easy to play. One day at a rehearsal, we swapped, and he was thrilled; he fell in love."

"I don't want anybody else to touch it," interjects Ikeda. "His wife is jealous," says Oundjian; their dialogue interlocks in the kind of counterpoint they produce so often on their violins.

The Tokyo's Amatis cannot really be called a matched set; they were made, for various purposes, over a period of 21 years. But "They do blend beautifully," Oundjian says.

The same can be said of the quartet's members, who are hardly identical in personality but highly compatible. This is essential in a musical relationship that violist Kazuhide Isomura says "is sort of like marriage -- without sex." Isomura apparently favors that kind of imagery; he has described playing on a borrowed viola as "like forbidden love."

Oundjian, the second replacement in the personnel of the Tokyo Quartet, is 10 years younger than the others. He has been a member of the group (which is celebrating its 15th anniversary) for five years. The four original members of the quartet began playing as a group when they were students at the Toho Music Academy in Japan in the 1960s. They were discovered there by the Juilliard Quartet, which arranged for them a collective scholarship to the Juilliard School and then nurtured and polished them into one of the world's finest musical ensembles.

The first member of the original group to leave was second violinist Yoshiko Nakura, who was replaced by Ikeda in 1974. When the original first violinist, Koichiro Harada, left the group in 1981, the other members seriously considered disbanding. Oundjian not only helped to keep the group together but subtly changed its musical impact, bringing an added sense of lyricism and expressive freedom without undermining the Tokyo's proverbial precise discipline.