August's quietude broken by a French musical and a moving revival. 'La Cage' is skillful, glittering, but flawed, while 'Corn Is Green' is still valid - and touching

The Broadway theater season begins officially in June, comes fitfully to life in the summer months, and gets down to serious business after Labor Day. The 1983-84 season thus far has been no exception. The July quietude was broken by the unexpectedly early arrival of madcap ''Mame'' - alias Angela Lansbury - in a merry re-creation of the 1966 Lawrence-Lee-Herman collaboration. August has brought the musical version of a French stage hit-turned-movie and a revival of Emlyn Williams's ''The Corn Is Green.'' La Cage aux Folles Musical comedy by Jerry Herman (music and lyrics) and Harvey Fierstein (book), based on the play by Jean Poiret. Directed by Arthur Laurents. Choreography by Scott Salmon. Starring George Hearn and Gene Barry.

It began as a Parisian boulevard comedy hit. Then came international popularity in two film versions. And now ''La Cage aux Folles'' has reached Broadway as a $5 million musical extravaganza with more beads, bangles, sequins, and rhinestones than you could shake a feather boa at.

While superficially ''daring'' in theme, the American adaptation at the Palace Theatre is, in its own peculiar way, as lush with sentimentality as an old-fashioned Valentine. Yet the romantic case it makes for homosexual relationships is one to which many playgoers will take exception.

At the center of all the glitz and glitter are the remarkable performances of George Hearn and Gene Barry. Mr. Barry plays Georges, the impresario of the St. Tropez night club from which the show takes its title. Mr. Hearn portrays Albin alias Zaza, the aging drag-queen star of the establishment with whom Georges has had a 20 year-homosexual relationship.Jean-Michel, the son whom Georges fathered in a youthful brief encounter, becomes engaged to the daughter of a politician conducting a morals campaign.

When it comes to presenting his future in-laws, the young man insists on a masquerade that will transform Georges into a respectable diplomat while banishing Albin entirely from the domestic scene. The bizarre consequences of the improvisation provide the comic denouement to Harvey Fierstein's adaptation.

Without performances as adroit and maturely seasoned as those of Messrs. Hearn and Barry, ''La Cage aux Folles'' would lose the elements of humanity and human vulnerability inherent in an admittedly confused view of life and relationships. Mr. Barry's Georges is that familiar contemporary personality, the gay male who can pass for straight. Mr. Hearn, without ever going camp, projects the comic pretensions and inner tensions of a character who is part drag queen and part mother hen. Even flouncing, Albin retains his dignity. Albin/Zaza expresses the subtheme of ''La Cage'' in the climactic first-act finale, ''I Am What I Am.'' However much one disagrees with its implications, the declaration is moving.

''La Cage aux Folles'' does, however, run into technical trouble in the second act. In contrast to his earlier restraint, director Arthur Laurents lets vulgarity run amok, both in the hamminess of some performances and in the burlesqueries of the big second-act production number.

But the show employs the arts and skills of the Broadway musical with consummate showmanship. Jerry Herman's score revels in more of those stairway numbers that embellished ''Hello, Dolly!'' and ''Mame.'' Mr. Herman has once more written several tunes of the kind that wind up as pop standards on the hit parade. They are beautifully served by Donald Pippin's vocal arrangements and musical direction and by Jim Tyler's Gallic-touched orchestrations.

Design and spectacle have been attended to with dazzling expertise by David Mitchell (St. Tropez scenery), Theoni V. Aldredge (yards and yards of eye-filling costumes), and Jules Fisher (lighting that modulates from glare and glitter to moonlight glow). Scott Salmon's choreography for ''Les Cagelles'' ranges from the elegant posturings of the floor-show dress parade to the athletic routines that turn dancers into acrobats.

The principals of ''La Cage'' include John Weiner (the callous Jean-Michel), delectable Leslie Stevens (his fiancee), Jay Garner and Merle Louise (the girl's crudely caricatured parents), as well as Elizabeth Parrish, William Thomas Jr., Walter Charles, and Brian Kelly. The Corn Is Green Comedy by Emlyn Williams. Directed by Vivian Matalon. Starring Cicely Tyson.

The theme of ''The Corn Is Green'' is as valid and relevant today as when this moving dramatic comedy first came to the stage more than 40 years ago. In a play with autobiographical references, Emlyn Williams was dealing with the kind of relationship that can change a life - the relationship between a determined, dedicated teacher and a brilliant student.

Miss Moffat is such a teacher. A Victorian spinster with more than a touch of the Shavian new woman about her, Miss Moffat comes to Glansarno, a remote Welsh village determined to improve the lot of the local children by starting a school. She is direct, outspoken, undiplomatic, and undaunted. But when the local powers-that-be - personified by the preening squire - present seemingly insurmountable obstacles, Miss Moffat decides to surrender. At that point, the crude eloquence of an essay by Morgan Evans, one of her miner-pupils, changes her mind and changes his life.

The reading of that small essay is still one of the moving high points of ''The Corn Is Green.'' There are other stirring passages, and much local comedy, in the Williams tribute to a redoubtable woman. Unfortunately, in the production staged by Vivian Matalan, the work's contrivances have not been well compensated for in performance.

Cicely Tyson is an exceptionally fine actress, but her vision of Miss Moffat's sincerity and singlemindedness seems constrained and uncertain. Nor does the English accent the actress has adopted help the situation. Miss Tyson seems uncomfortable in the role.

Mia Dillon gives a thoroughly saucy performance as the sly, self-willed wanton whose seduction of the momentarily susceptible Morgan almost wrecks his chances. Peter Gallagher is appealingly straightforward as the talented young miner for whom the mine becomes the symbol of the intellectual darkness from which he is struggling to escape.

The play's sturdy qualities are reasonably well captured by a cast that includes Elizabeth Seal, Gil Rogers, Frank Hamilton, and Marge Redmond. The production at the Lunt/Fontanne Theatre was designed by William Ritman (setting) , Theoni V. Aldredge (costumes), and Richard Nelson (lighting).

''The Corn Is Green'' is the second production by the recently formed Elizabeth Theatre Group (Zev Bufman and Elizabeth Taylor).