''Present Laughter'' is filling the deep reaches of the uptown Circle in the Square with sounds of pleasant mirth these warm summer evenings. With George C. Scott as star and director, the 40-year-old farcical comedy proves as durable as it is antic. A vote of thanks to Noel Coward, that inimitable voice from the past, for giving Broadway's comic stock a much-needed boost.
Mr. Scott's Garry Essendine is in every respect a substantial thespian. Even at his most ridiculously temperamental, the Scott Garry is never less than formidable and imposing. Mr. Scott clearly delights in Garry, from his acidulous , raspingly delivered witticisms to what Cole Lesley called the ''histrionic bravura'' of the third-act tirade. Garry's dalliances are momentary, incidental distractions from his central preoccupation with the main event: himself.
On the other hand, director Scott recognizes that Coward's incidental comic characters are anything but distractions. They are intrinsic to the apparently ever more frantic comic scene. A staging alive with physical action takes particular delight in contrasting the snail-like passages of Bette Henritze's Scandinavian Miss Erikson with the sprints and dartings of Jim Piddock's Fred, the former ship's steward. Equally vital to the slice of Garry's this-is-
your-life are the impetuously determined debutante, Daphne, of Kate Burton and Nathan Lane's manic Roland Maule.
The principal supporting players in a spirited cast include Dana Ivey (Garry's indispensable secretary), Elizabeth Hubbard (the infallibly sage Mrs. Essendine), and Christine Lahti (the predatory seductress, Joanna Lyppiatt). Richard Woods and Edward Connery oblige as the utility plot props required of such boulevard capers. In terms of accent, this ''Present Laughter'' might be described as mid-Atlantic with variation.
The physical production is something of a disappointment. Marjorie Bradley Kellogg's pre-World War II setting seems a bit too institutionally art deco. Ann Roth's costumes - even Garry's wardrobe of dressing gowns - are curiously unchic. These are shortcomings in a revival which, while it may not achieve virtuosity, offers an enjoyable assortment of comic virtues. Richard Nelson lighted the production, and the incidental piano music is from the Coward treasury.