Barbara Cook, in concert at the Terrace Theater through Aug. 30. Musical director: Wally Harper. Also appearing: The Manhattan Rhythm Kings.

Barbara Cook is one of those singers whose fans are fervid, bestowing their loyalty as a vassal would vow fealty to a lord. She is an extraordinary singer, as her opening last night in the Terrace Theater amply demonstrated.

She is, of course, something of an acquired taste, as not everyone responds to the marriage of pop music to her quasi-operatic, dramatic soprano. Those of us who do respond know it isn't just her voice that draws, but Cook herself, and her ability to sing the words as well as the melody.

She has a special quality of communicating what the song is saying, through her clear diction, phrasing and acting ability. Aided by the imaginative and inventive arrangements by Wally Harper, who also played the piano and sang harmonies, Cook segued easily from songs like Harry Nilsson's "Remember," to "Paper Moon," to one of her old crowd-pleasers, "Wait Till You See Him," a virtuoso display of breath control.

Looking quite sexy in a black jumpsuit and sequined coat, she handled her ever-adoring audience with cheerful aplomb. Last night's performance was a benefit for the Gertrude Stein Democratic Club, a gay political organization. In addition, Effi Barry, wife of the mayor, was there to pronounce yesterday Barbara Cook Day in Washington.

The Terrace Theater, where Cook will be for the next two weeks, seems a good home for her. It's more intimate than the cavernous Opera House, where she played her first concert engagement here, and less intimate than the tiny Door (formerly the Cellar Door) or the now-defunct Waaay Off-Broadway, where she has also performed.

Cook was preceded by a remarkable trio called the Manhattan Rhythm Kings, a group that models itself after Paul Whiteman's Rhythm Boys and the Boswell Sisters. Wearing fedoras and brown-and-white spectator shoes and jackets with shoulder pads a la the 1940s, they spun through a collection of numbers that included "Shanghai Lil" and the Rice Crispies song ("Snap, Crackle, Pop," remember?).

Lead singer Michael Reeder also tap danced and played several saxophones and cymbals; David Lisker (the one with the mustache and the guitar) also sang and Brian Nalepka not only played the bass but also made a noise like Tarzan. What more could you want?