Ever a Huckleberry Friend, Come Rain or Come Shine.

To attend an Andrea Marcovicci cabaret show is to participate in a communal rite in which it is tacitly understood -- at least during the duration of the performance -- that nothing today can match the magic and romance of old Hollywood and Broadway. An audience of a certain age agrees to gorge retrospectively on the illusions of youth from an era long before the proliferation of viral gossip and reality television. As the ceremonial priestess, Ms. Marcovicci plays a grand, smiling Hollywood hostess -- a Loretta Young-like figure -- throwing open doors to a rose-colored mythology. Her new show, ''Skylark: Marcovicci Sings Mercer,'' at the Oak Room of the Algonquin Hotel, a tribute to the songwriter Johnny Mercer, who would have turned 100 on Nov. 18 (Ms. Marcovicci turned 61 the same day), should perpetuate her reign as the queen of high-class cabaret nostalgia. At the opening-night show last week, Ms. Marcovicci, who is celebrating her 23rd year at the Oak Room, once again worked her wiles as a show-business medium channeling Olympian spirits. Mercer may have had a drinking problem -- when in his cups, she said, he once told Irving Berlin that he ''couldn't write his way out of a paper bag'' -- but it was a minor quirk in her otherwise hagiographic account of his life. [ABSTRACT FROM PUBLISHER]