As managing director of the Washington Performing Arts Society, Patrick Hayes certainly doesn't have to sell tickets to the Friday evening chamber music concerts at the Library of Congress. But for 27 years, beginning at 8:30 a.m. on the Monday before each concert, he has done so personally.

"I'd rather do it myself," Hayes says, tracing his enjoyment to a job he "never got over" as a counterboy in a West Brookfield, Massachusetts country store. "I meet a lot of people and welcome newcomers to town."

At 25 cents a ticket -- a service charge -- concerts at the Library are one of the great Washington bargains. But it's choice of seats, not cheapness, that leads music lovers to form a line an hour or two before Hayes unlocks the door and turns on the lights at Jordan Kitt's, 1330 G Street NW.

"I've seen them in rain and sleet and subfreezing weather," said multimedia producer Steve Spector, who attended his first Library concert 12 years ago when he was a Bethesda high-school student.

A savvy veteran, he brings a folding director's chair to set up on the sidewalk. "It's not paying so little," he said, "it's what you have to do to pay so little." Waiting in line "takes a commitment to the music."

Often one of the first to arrive on Monday mornings is George Pappas, a retired Air Force intelligence officer who met his future wife while waiting for tickets in 1952, saw her again after returning to the ticket line from a three-year stint in Bangkok and married her in 1967.

"I'm spoiled. I've heard the best," Pappas said. "If you've heard the Budapest, the Juilliard and the Beaux Arts," he went on, referring to the Library's first and current resident quartets and its resident trio, "what more could you ask?"

Well, how about Artur Rubinstein, Andre Watt, Claudio Arrau and Rudolf Serkin? All have played the Library, as have Gregor Piatigorsky, Pierre Fournier and Leonard Rose, not to mention Yehudi Menuhin, Itzhak Perlman and Zino Francescatti.

Menahem Pressler, pianist of the Beaux Arts Trio, puts it simply: "This is the mecca of chamber music."

The Coolidge Auditorium has much to do with the Library's prestige. Built specifically for chamber music in 1925 with funds donated by Elizabeth Sprague Coolidge, the 511-seat hall falls short only of the "severe and chaste beauty" she envisioned. To call it plain would be charitable.

The hall's design is exemplary in every other respect. The rows are so well-pitched there isn't a bad seat in the house, and because the auditorium is shallow, Hayes might have been referring to any seat the morning he offered a pair of tickets and remarked, "How 'bout the front row. Shake hands with the musicians."

The acoustics draw raves. "It's the dream of every performer," said Beaux Arts cellist Bernard Greenhouse, who said the house plays like a Stradivarius. "We always speak of this hall as one of the finest in the world."

"Every note has a halo around it," Pressler said. "It's a kind of magic."

Adjoining the Coolidge Auditorium is the Whittall Pavilion, gift of Gertrude Clarke Whittall in 1938 and waiting room for those who, depending on their place in line on concert night, receive either the tickets returned to the box office or the seats of no- shows after the first piece of the evening.

Standing in line thus is inescapable, but there is no service charge for admission through the pavilion, and if the tickets run out there are chairs and sofas where one may watch the concert on closed-circuit TV.

The pavilion is also the showcase of Whittall's priceless gift of Stradivari instruments -- an uncustomary quintet of three violins, a viola, and a cello, all made between 1699 and 1727 -- and Tourte bows.

The instruments must be played to maintain their tone. Because few artists feel comfortable with unfamiliar instruments, the Library invited the Budapest to play 20 concerts on the Strads in 1939.

The Budapest must have grown comfortable with the instruments, for it remained in residence until 1962, becoming the only group during its tenure to play them.

"Nobody ever played Beethoven the way the Budapest did. It was unbelievable," said Pappas, who recalls getting up at 4 a.m. one Monday for tickets to hear them.

"Greatest quartet in the world," said Ben Soffer, a Commerce Department economist.

"They really brought a name to this place," said Elmer Booze, a senior reference librarian in the Library's music division and, for 15 years, page-turner for the pianists.

The regulars share the Budapest's tradition of musical excellence and longevity, being a compact group who are, says Booze, "extremely receptive to music-making."

"The audiences are as varied in background and sincere in enjoyment as I have experienced anywhere," said retired VA and SEC employee Anson Courter, who "strolled into the Library of Congress by accident in 1936 and got hooked."

"It's really an elite bunch," said Harry Merican, who met Courter at the VA in 1936 but didn't stumble on the concerts himself until 1947. "There aren't so many of us left anymore," he added.

The artists there are both established musicians and young performers of the highest caliber. The programs are rich with Beethoven, Mozart, Haydn and Schubert, and include a smattering of contemporary music, some of it commissioned to premiere there.

But it is the Juilliard Quartet, heir to the Budapest, that has become synonymous with chamber music at the Library.

Now in its 21st year of residence, the Juilliard is one of the world's most dynamic chamber groups. In a recent Library publication first violinist Robert Mann wrote that chamber music for his group "burns with life. We'll play a piece we hope sounds so exciting, so engrossing, that you'll say, 'I didn't know chamber music was like that.' "

It's not too late to hear tonight's program, the Juilliard's third of the spring. Capitol South Metro station is closest to the Auditorium, which is in the Library's main building at First Street and Constitution Avenue SE. Union Station is a short jog away and any "30" bus will take you to the Library from Pennsylvania Avenue downtown.

To play it safe, arrive by 6:30 p.m. Sandra Key of the music division says the first 60 in line usually get in, but the number may be smaller for the Juilliard, which will be playing the Strads tonight tonight in a program of three Beethoven quartets.

Of the 16 quartets Beethoven wrote, you'll hear the 12th and Second before intermission, the Eighth after. Named the Rasumovsky No. 2 after the Russian count who commissioned it, the Eighth contains in its third movement a Russian tune that Rasumovsky asked the composer to incorporate, or so the story goes. It was a favorite of the late Abe Fortas, former Supreme Court Justice and a gifted violinist, who found playing it "particularly rewarding."

Go to the Library early and see the Great Hall and the dome of the Main Reading Room. They don't get as much play as other sights in the city; you'll wonder why.