The Sigmund Romberg centennial may not be a big item in this year's arts agenda, but it was celebrated with fervor at the Smithsonian last night, with a performance of reminiscences and songs. William R. Osteck, who emceed the affair, is a true believer whose rich mixture of colorful facts and apocrypha, delivered in a style that brought to mind both Jimmy Durante and Casey Stengel, climaxed in a shout of, "Long live the music of Sigmund Romberg!" The vocal quartet responded with a reprieve of "Stout-Hearted Men" and the audience lapped it up.

The show was the creation of the Center for the American Musical, based at Canada College in Redwood City, Calif., and of its director, Joe Marchi. Musically speaking, its star was accompanist Dawn Horst, who held it together, provided continuity and followed every vocal nuance with ease.

Of the singers, baritone Warren Brown and soprano Julia Lee Jepsen seemed most in command of the vocal demands of the music, and seemed least tired at the end. Tenor Peter Stephen Lewis had a tendency to bellow at the top of his range, and soprano Kathleen Simas Young sang with tremendous vibrato and unfortunately pinched sound.