To some, he is New York City personified -- Bobby Short, the eternally youthful singer and pianist who has been packing in audiences at the Cafe Carlyle five nights a week for the past 11 years. Regarded as the foremost living interpreter of Cole Porter, Short has recorded eight albums, published his autobiography, lectured on American music at Harvard and performed at the White House. His many television commercials have gained him national recognition in the last year or so, but he is proudest of the one he did for the "I Love A Clean New York" campaign, showing him sweeping the sidewalk with his customary savoir-faire. Six months out of the year, he holds court at the Carlyle, a supper club at Lexington Avenue and 76th Street, where eager fans plunk down $10 for each one-hour set. Backed up by a bass player and a percussionist, the smooth, sophisticated Short sits behind the keyboard in a tuxedo, performing popular songs from the early 20th century to the present day. Every word and every note comes out a finely polished jewel, leaving the audience with the impression that they have never heard the song before. Four months out of the year, Short takes to the road, giving concerts from Los Angeles to Paris, often as soloist with major orchestras. The hottest and coldest months of the year -- January and August -- he sets aside for vacation, sometimes taking a house in the south of France, since he is well versed in the French language and is constantly seeking to expand his knowledge of gourmet cooking. While in New York, he occupies a luxurious nine-room Westside apartment with 18-foot ceilings that formerly belonged to Leonard Bernstein. Here, in a vast living room with a complete wall of mirror, a fireplace and a virtual forest of green plants, I thank Short for the glass of wine that he offers me from a crystal decanter, and I begin our interview by asking about the show he's co-producing for the Newport Jazz Festival. Titled A _Salute to Black Broadway, 1900-1945_, it will take place in Avery Fisher Hall at 8 p.m. on June 24, and is one of the highlights of the 26th annual jazz festival, which runs from June 22 to July 1. "It's the chance to try my wings at something new," says the jovial musician, in a somewhat gravelly, high-pitched voice marked by flawless diction. "Also, it's a chance to inform. I suppose I'm a frustrated professor of sorts. This show is a way of stating that, in fact, there were blacks involved in productions on Broadway as far back as 1900 -- perhaps even further back. Many were performers who wrote their own material. Others were composers and lyricists whose writing was not confined to black performers. Some of them wrote for the Ziegfeld Follies."