Arnold Sundgaard, a lyricist, librettist and playwright who collaborated with some of the most distinguished artists of the 20th century, died on Oct. 22 at his home in Dallas. He was 96.

As a lyricist, Mr. Sundgaard wrote numerous songs and libretti for a dozen operas, working with some of the leading composers of the day, including Kurt Weill (“Down in the Valley”, 1948) and Alec Wilder. With Wilder, he wrote several songs, including “How Lovely Is Christmas,” that appear on the album “Bing Crosby’s White Christmas in Story and Song,” released last year. In 1952, he wrote the libretto for Wilder's opera, “The Lowland Sea.” Sundgaard also wrote the libretto for Douglas S. Moore’s “Giants in the Earth,” an opera based on the novel by O. E. Rolvaag. Moore’s score won the Pulitzer Prize for music in 1951.

As a playwright, Mr. Sundgaard saw a half-dozen of his works come to Broadway, including “Of Love Remembered” (1967), directed by Burgess Meredith and starring Ingrid Thulin. He was perhaps better known as the author of “Spirochete: A History,” an impassioned drama with more than 70 different speaking parts about the war against syphilis, which caused a sensation when it was produced by the Federal Theater Project in 1938.

Sundgaard held degrees from the University of Wisconsin and Yale Drama School. He later taught drama at several colleges and universities, among them Columbia, Bennington and the University of Texas.

In recent years, Mr. Sundgaard turned to writing children’s picture books. Here too, he had an eminent accomplice, the noted illustrator Eric Carle, with whom he did “The Lamb and the Butterfly” (Orchard Books, 1988). Mr. Sundgaard also wrote “The Bear Who Loved Puccini” (Philomel, 1992), illustrated by Dominic Catalano