MUSICIANS and critics aren't inclined to say nice things about Barbara Cook's voice. They're inclined to gush with superlatives.

Over the years Cook has had everyone from Leonard Bernstein to Rex Reed thumbing through the dictionary in search of the right words to describe her voice. "Glorious," "lucid," "sure" and "powerful" are common choices -- adjectives which occasionally seem to outnumber the nouns and verbs in her reviews.

Beginning Tuesday, Washingtonians will get a chance to judge for themselves when Cook and the Manhattan Rhythm Kings open at the Kennedy Center Terrace Theater, with performance scheduled through Aug. 30th. For those who can't make it, however, Cook's latest album, "It's Better With a Band" (MMG-104), is a wonderful example of the singer at work. It was recorded live last fall before an adoring audience at Carnegie Hall.

Cook's voice, for all its range and clarity, isn't solely responsible for the power she projects on stage. Many of her fans obviously remember her early Broadway triumphs, often playing the blonde, blue-eyed ingenue in such musicals as "Candide," "She Loves Me," "The Grass Harp," and especially "The Music Man" in the role of Marion the Librarian.

Even on a recording you can feel the enormous affection and admiration that she has accrued. When she makes her entrance, with the orchestrated fanfare reaching a crescendo behind her, the crowd lets out a roar so you'd think she just returned from the dead. This is no pleased-to-see-you reception, and Cook is no prim and proper soprano.

"Lordy Me!," she says with just a trace of a Georgia drawl before gliding ever so elegantly into Irving Berlin's "I Love a Piano." It's no doubt true that Cook has always belonged on Broadway. Her voice is so big and robust, her phrasing so articulate, that a less demanding setting simply doesn't do her justice. But it's also true that Cook hasn't wasted her time or talent singing in cabarets recently.

Working with her composer-arranger-accompanist Wally Harper, she has developed and mastered a delightfully eclectic repertoire, full of unexpected changes in mood and tempo. In Berlin's words, Cook likes to "meddle with music," and she begins immediately, winding up "I Love a Piano" as if it were the high-kicking finale to "New York, New York."

"It's Better With a Band," the title track, juxtaposes her voice with virtually every instrument in the orchestra at one point or another. It's the kind of arrangement that would tax the talent of a less gifted singer in no time at all.

Cook then moves from the sublime to the meticulous on a medley of contemporary ballads by Harry Nilsson and Melissa Manchester. Nilsson's "Remember" is warm and reflective, while Manchester's "Come in From the Rain" sounds remarkably fresh and vital despite its familiarity.

Even more surprising is her treatment of the rather ordinary lyric, "Singing a Song With Me." Cook combines it with "Chant La Vie" and the resulting medley, much of it sung in French, builds considerable momentum.The one song, however, which best captures the joie de vivre of this recording is "Them There Eyes."

The opening verse suggests a torch song at first, but Cook is soon cast opposite Sam Pilafin's playfully strutting tuba, and her mood becomes increasingly vivacious. Taking her cue from a banjo player who lends a festive air to the proceedings, the singer grabs hold of a kazoo and marches all of the musicians home as the crowd cheers on the parade.

The purity, strength and agility of her soprano is best revealed later in a lengthy tribute to Leonard Bernstein, ranging from an exquisite "Simple Song" from Bernstein's "Mass" to the sassy "I Can Cook, Too" from "On The Town." On these numbers you can appreciate not just beauty and relative clarity of Cook's upper register, but her accomplished delivery as well.

You also have to appreciate her self-effacing humor, particularly on the Gilbert and Sullivan-inspired "The Ingenue." Wittily summing up her Broadway experiences, Cook goes so far as to remind the audience that she lost out to Shirley Jones when "The Music Man" was made into a film. Professional setbacks aside, Barbara Cook can take pride in knowing that there are few voices, on or off Broadway, to match hers.

Opening for her will be the Manhattan Rhythm Kings, making their Washington debut. Their new album "The Manhattan Rhythm Kings (Inner City IC 1124) is an ingratiating blend of popular ragtime pieces, jive tunes and vaudeville novelties all delivered with style and a minimum of fuss. This tap dancing, kazoo-playing male trio of singers works hard to recall the sound of the Boswell Sisters, the Mills Brothers and early Bing Crosby. With a catalogue of songs that includes "Happy Feet," "When You Smoke That Killin' Jive" and "Snookie Ookums" they shouldn't have any problem enlivening Cook's concert. In addition to the Kazoos, the Rhythm Kings, who favor pleated pants and felt hats, will also bring with them a small arsenal of wind and percussion instruments.