Coward, Fugard, and Shaw grace New York stages Hay Fever Comedy by No"el Coward. Starring Rosemary Harris. Directed by Brian Murray.

How better could blithe make-believe celebrate the Christmas season than with a No"el Coward classic? Producer Roger Peters and the debuting MBS Company have answered the rhetorical question with ``Hay Fever.'' The dashing revival of Coward's romping 1925 satirical farce fills the Music Box with the sound of the cuckoo and the bubbling music of laughter. A London success that failed the first time around in New York, ``Hay Fever'' has achieved the status of comic creations that survive and thrive beyond their own times and fashions. The stylish Music Box production recaptures the attitudes of a bygone era as Coward delineates the ordeals endured by four weekend guests at the Cookham country home of the egocentric, bad-mannered Blisses.

Incomparable Rosemary Harris stars as the slightly pass'e luminary Judith Bliss, who knows more about stealing a scene than she does about the flowers at the bottom of her garden. A picturesque putterer, Judith couldn't tell a delphinium from an aster, which she thinks is an aristocratic family name. And she would be the last to suspect that the Bliss family flower is probably the narcissus. Miss Harris gives us every toss of Judith's lovely head, every last affectation, and every trick of the grand man ner and the vocal glissando.

Mia Dillon and Robert Joy revel in the roles of the Blisses' spoiled and tempestuous offspring, the objects of their mother's occasional bouts of maternalism. The family foursome is completed by Roy Dotrice as pop-author David Bliss. They are antically served by Barbara Bryne as the maid-of-all-work who has graduated (at least temporarily) from theatrical dresser to suburban domestic. The neglected weekend guests, whom the Blisses have invited without consulting each other, are gamely played by Charles Kimbrough as a starchy diplomat, Campbell Scott as one of Judith's adoring young fans, Carolyn Seymour as a catty social gadfly, and Deborah Rush as the pathetic and ultimate dumb blonde.

The set pieces of ``Hay Fever'' -- the ``welcoming'' tea party, the riotous adverb game, the morning-after breakfast and mock melodramatic climax -- come off with unalloyed hilarity. Jennifer von Mayrhauser's costumes are delightfully '20s chic. Michael Yeargan has designed a country house drawing room (lighted, come rain or shine, by Arden Fingerhut). Its hospitable amenities belie the heedless inhospitality of the hosts. In contrast to the deplorable state of bad manners in the Bliss household, the state of play at the Music Box is comically Blissful. The Blood Knot Play by Athol Fugard. Starring Zakes Mokae, Mr. Fugard. Directed by the author.

Each clasping the other's hand, Zakes Mokae and Athol Fugard raise arms in a salute -- to an applauding audience, to a moment of elation, and to what the occasion signifies. The two actors have just finished a performance of ``The Blood Knot,'' the moving and frequently comic Fugard drama the two men first acted in 1961 in South Africa. Since that breakthrough work, the association between the internationally acclaimed playwright and one of South Africa's major acting talents has become part of 20 th-century theatrical history.

The stirring curtain calls at the Golden Theatre acclaim the first Broadway production of ``The Blood Knot.'' (It was acted Off Broadway in 1964 by James Earl Jones and J. D. Cannon.) Mr. Fugard staged the present Yale Repertory Theatre revival.

``The Blood Knot'' concerns the relationship between two half-brothers, the black Zachariah (Mr. Mokae) and the light-skinned ``Colored'' Morris (Mr. Fugard), whose father was a white man. After passing as white for a number of years, Morris has returned to Zachariah's one-room shack in the nonwhite shanty town of Korstein, near Port Elizabeth. Morris seizes on the uneasy reunion to ingratiate himself with the somewhat skeptical Zachariah, a gate tender at a local whites-only park. Besides performing do mestic chores, fussy Morris takes custody of his half-brother's wages, explaining that the money saved will enable them to make a down payment on a small farm.

When Zachariah complains about lack of female companionship, the resourceful Morris finds him a ``pen pal'' in a local newspaper and serves as amanuensis for his illiterate half-brother. The pen pal turns out to be a white woman who soon writes that she plans visiting Port Elizabeth and looks forward to meeting her correspondent. Zachariah's solution to the alarming prospect -- that Morris keep the rendezvous dressed in a brand new outfit of second-hand clothes -- proves unnecessary. The comicality of t he situation yields to an underlying poignancy and an ultimate realization of brotherly solidarity.

Whether treated overtly or indirectly, South Africa's racial crisis is at the heart of ``The Blood Knot.'' Nothing that has happened in the quarter-century since the play was first performed has altered its relevance or diminished its triumphant spirit. The curtain calls at the Golden respond not only to the illuminating performance but to the deeper emotions and implications of the event. A 1982 Tony Award-winner for his work in Mr. Fugard's ``Master Harold . . . and the boys, '' Mr. Mokae endows Zachariah with the innate dignity of an individual whose subjugation has not robbed him of humanity or humor. Mr. Fugard perceives Morris as a man of uncertain status, whose search for his own identity begins with the effort to reinstate himself with his half-brother. The shanty setting for the action has been designed by Rusty Smith, with lighting by William B. Warfel, and costumes by Susan Hilferty. The limited engagement of ``Blood Knot'' is scheduled to end on Feb. 28. Mrs. Warren's Profession Comedy by George Bernard Shaw. Starring Uta Hagen. Directed by John Madden.

For the second production of its 20th-anniversary season, the Roundabout Theatre Company has come up with a fresh and vigorous revival of ``Mrs. Warren's Profession.'' Although the social context of what he termed an ``unpleasant play'' has changed radically in the 92 years since George Bernard Shaw wrote it, the fundamental conflict remains relevant. In the end, Shaw pits the greed and hypocrisy of a society that condones its self-indulgent vices against the moral and intellectual integrity that refuse s to compromise.

The conflict of this absorbing dramatic comedy centers on the reunion of Mrs. Kitty Warren (Uta Hagen) with her illegitimate daughter, Vivie (Pamela Reed). Vivie is unaware that the affluence in which she lives, not to mention the Cambridge education that has made her a first-class mathematics scholar, has been financed by Kitty Warren's success as the partner in a chain of European brothels. Shaw naturally uses the occasion to satirize various other aspects of Victorian society. But the big scenes betw een Kitty and Vivie -- notably their moving reconciliation and subsequent bitter showdown -- provide the dramatic high points of ``Mrs. Warren's Profession.''

Shaw describes Mrs. Warren in part as: ``Rather spoiled and domineering, but, on the whole, a genial and fairly presentable old blackguard of a woman.'' Miss Hagen and director Johm Madden have taken the author at his word. Resplendent in feathers and furbelows and an enormous picture hat, Kitty sweeps onstage as a woman who knows how to dazzle and command. Miss Hagen stresses the vulgarity of the erstwhile prostitute with a slight Cockney twang and an extrovert heartiness. Having risen from abject prov erty to financial independence, she is a match for any man on the premises -- but not for the impervious Vivie.

As a variant of the Shavian New Woman, the actress playing Vivie must make it clear that her motivating level-headedness and unsentimental independence are quite apart from the priggishness of which she is accused. Miss Reed manages the distinction in a performance that combines clarity, humor, and genuine perception. One of the theater's most gifted young actresses is giving one of her finest performances.

Although one may quibble about the somewhat variable accents of the revival, it never lacks the histrionic energy level essential to the momentum of a Shavian performance. The dependable Roundabout cast includes George Morfogen as the intensely aesthetic Praed, Harris Yulin as the brutally cynical Sir George Crofts, William Converse-Roberts as Frank Gardner, Vivie's adoring but feckless boy next door, and Gordon Sterne as Frank's father, the muddle-headed pastor whose past indiscretion provides the come dy with its most startling dramatic surprise.

The airiness of the revival is matched by Andrew Jackness's simple but attractive setting, brightly illumined by lighting designer Frances Aronson. Nan Cibula has costumed the actors handsomely in period.