Founder's Day at the Library of Congress was cause for celebration last night as Ned Rorem played and Phyllis Byrn-Julson sang two cycles of his songs, one of them a world premiere commissioned for the occasion.

Marked annually on the birthday of Elizabeth Sprague Coolidge, Founder's Day has, over the years brought out new works that have soon thereafter entered the standard repertoire. It is likely that Rorem's new cycle, Nantucket Songs will quickly be taken up by sopranos with the voices and the brains to handle it. They are a rare breed.

As the character of the poems in the Nantucket cycle is more lyrical than that Women's Voices, the cycle that opened the concert, so Rorem has framed his newest songs with lyrical grace. He has, among other notable gifts, a genius for capturing in 16 measures -- as in his setting of Christina Rossetti's "Ferry Me Across the Water" -- the spirit of an exquisite miniature and giving it new life through his equally exquisite music.

Dance appeared in widely differing guises in Nantucket Songs. Rorem sets William Carlos Williams' poem about Breughel's painting, "The Kermess," in a big, boisterous waltz, which he prompltly follows with an evocative, languorous waltz for Williams' "Natucket."

Placing the two cycles on a single program demonstrated the many facets of Rorem's writing that have, for three decades, kept his songs on the highest level.

There is shock and fear as well as bitter gloom and resignation in writings left by women over a period of 400 years. Two of many noteworthy moments in Women's Voices are the toccata for Mary Hebert's lament over the death of her brother, and Mary Chudleigh's observation that a wife is a servant in all but name.

The ultimate glory of Rorem's songs is his recognition of the potential of the voice, which leads him to write the great soaring phrases that have always thrilled singers and audiences.

He was extraordinarily fortunate last night in the presence of Bryn-Julson, the precise beauty of whose enunciation made composer's rich selection of poems the more appreciated.

In two Debussy cycles, Fetes glantes, and the Mallarme poems, both piano -- in touch and pedaling -- and voice explored all the sensuous pleasures. In so doing they brought to light compositional resemblances between the Mallarme songs and Women's Voices. It was a rich evening.