Born in Transylvania one hundred years ago, Bela Bartok is being given birthday parties all over the world. Last night was one of the more exciting ones, as the Juilliard String Quartet played his even-numbered quartets at the Library of Congress.

Bartok's music gave substance to the bourgeois illusions of nationalist folk art. With weakened tonal foundations through diminished fifths and jarring melodies, the pallor of his musical colors often sang of loneliness in a changing world.

Nowhere was this song more frantic than in the opening of the Quartet No. 4. It was taken a bit deliberately last night, the noisy edges of the glissandi not quite reckless enough to astonish. But there was fire forthcoming, as the ensemble attacked the unusual allegretto pizzicato third movement with machine gun precision. The effect was violent and exciting, and the mood remained the same through the breezy final pages, where Robert Mann's violin sang out with gypsy brio. At the end, the audience sighed.

There was also a bit of unscheduled excitement in the Quartet No. 2, which opened the program. The first few pages led uneventfully to the upper reaches of the cello's voice, breaking abruptly into the second movement. Here Bartok forced his music toward the ugly; the melodies were strangled, intonation was in doubt. The Juilliard Quartet responded to his every wish. It was a mad musical rush, with the ancestral ghost of folk music dancing an icy step as fine Stradivarius instruments were pushed to their limits. Then there was a gasp, a sound like ice breaking, and the Allegro turned to sadness as one of the cello strings snapped. Poor Joel Krosnick had to leave Coolidge Auditorium to replace it, but when he returned the playing was as fine.

The concert, which will be repeated tonight at 8, closed with the 1939 Quartet No. 6.