"Some people collect stamps, I collect old show tunes," says Steve Ross, pianist and singer, who sees himself as a "musical archivist." Today at 3 and 7:30 p.m. at the Natural History Museum's Baird Auditorium, Ross will perform "transatlantic" songs -- songs written by Americans for English musicals, and songs from English productions that traveled to America.

In this musical excursion across the "big pond," Ross sees the history of the transatlantic musical in cycles. "Prior to the '20s, America imported a lot of musicals from England. Then the tide began to turn and we started sending musicals to England and some of our composers even went over there, including Cole Porter." Now he sees that tide shifting back. "Some of the most popular shows are coming to America from England, like 'Cats,' for example."

Ross will perform songs ranging from "Never Mind the Why and Wherefore" from Gilbert and Sullivan's 19th-century "H.M.S. Pinafore" to "Think of Me" from Andrew Lloyd Webber's current hit "Phantom of the Opera," which hasn't yet landed on America's shores. Also on the bill, tunes from "Kiss Me Kate," "Me and My Girl" and "The Girl Who Came to Supper."

"When you hear the songs you get a feeling for the period in which they were written," Ross says. "Of course, these songs are the gems. I have boxes of sheet music I couldn't play because they're so boring."

Tickets are $10 for Smithsonian Resident Associate Program members and $15 for nonmembers. Call 357-3030 for information.