For more than 3 1/2 decades one of the happier truths of American life has been that the music of summer is jazz. Since 1953, when the Newport Jazz Festival made its debut, late June and early July have been the time when jazz emerges from the nightclubs and cafes and basks in the sunlight. That's just what it's doing right now, at the JVC Jazz Festival, which began last weekend at various venues in New York City and will end this weekend at more bucolic arts centers upstate in Saratoga and Finger Lakes.

The JVC shindig is the latest in a long line of linear descendants of the Newport Jazz Festival, which was run out of its birthplace a couple of decades ago; the crowds finally got too rowdy for Newport's city fathers, who'd never been especially comfortable with the festival in the first place, and they sent it packing. That it ended up in New York probably was both predictable and inevitable, but no matter how many riverboat rides and Finger Lakes excursions the festival's promoters stage, one certainty can't be escaped: New York isn't Newport.

Yes, they call the coming weekend's concerts "Newport Jazz at Saratoga" and "Newport Jazz at Finger Lakes," and no doubt the charms of those two communities will mix agreeably with the sounds of Gerry Mulligan and Sir Charles Thompson and McCoy Tyner and Marcus Roberts and other eminences. But though the Newport name has stuck doggedly to the festival as it's undergone heaven knows how many incarnations and transmogrifications, it was the Newport Jazz Festival only when it was in Newport.

Maybe you had to be there. But since you can't be, second best has suddenly, miraculously, become possible. Last week -- fittingly enough, on the first day of summer -- the mail brought a package that can be called long-awaited only at the risk of serious understatement. For years I had conducted an obsessive, impassioned and entirely fruitless search for a videotape of a movie called "Jazz on a Summer's Day." Then three weeks ago I opened the July issue of Down Beat and found, to my astonishment, an advertisement for just that; the check was in the mail faster than you can say "Jack Teagarden," and eight days later the tape -- which by that point had come to seem nothing more than a figment of my imagination -- was in hand.

"Jazz on a Summer's Day" is precisely what its title suggests: the record of a single day's jazz, from daybreak until after midnight. It was filmed by a photographer named Bert Stern in Newport in July of 1958, and upon its release about a year later was immediately, and deservedly, praised as the finest film yet made about jazz. But it was an art film about an art form, and soon enough it vanished; it had been at least a quarter-century between the last time I saw it in a theater and the first time I slipped the videocassette into the playback machine.

That many others will respond as passionately as I do to this movie is unlikely; not merely did I attend almost every performance of the Newport Jazz Festival during the first decade of its existence, but by 1958 my parents had built the small house five miles outside Newport to which eventually they retired; so the film's pleasures for me are at least as much personal as musical. But you don't need to recognize familiar places and scenes, some of them long gone and deeply mourned, to recognize the film's intrinsic qualities: its graceful intermingling of sound and setting, its affectionate eye for the people of jazz, and its incomparable depiction of the lost glories of Newport jazz.

The music alone is reason enough to love the movie. It opens with Jimmy Giuffre and Bob Brookmeyer, then works its leisurely way through a panoply that includes Thelonious Monk, Anita O'Day, Chico Hamilton, Chuck Berry -- yes, Chuck Berry -- Art Farmer, Mulligan and Louis Armstrong, reaching both its climax and its denouement in a post-midnight appearance by Mahalia Jackson that closes with a powerful (and, for the boisterous crowd, powerfully sobering) rendition of the Lord's Prayer. Viewed from the perspective of 1990, the movie gives us too little Monk and too much Hamilton, but that's about the only musical complaint; the sounds have passed the test of time as brilliantly as have the sights.

What beautiful sights they are. Stern understood, as too few others have, that the Newport Jazz Festival was sui generis: that it was this particular location that made the festival what it was, that there was a wholly unplanned and unexpected marriage between the music in the air and the deep blue seas only a few hundred yards away. Off in the Atlantic an America's Cup challenge was taking place that summer; Stern filmed the stately boats from the air, then accompanied these breathtaking pictures with the heavenly sounds being played on the stage at Freebody Park.

He also had a nice feel for the audience. From time to time he subjects us, without a trace of irony, to shots of peachy-keen preppies falling all over themselves trying to be hip; mostly, though, he captures the mood of genuine happiness that permeated the place, the relaxed intermingling of musicians and audience, the surprisingly unself-conscious encounters -- this, bear in mind, was 1958 -- between black and white. Only one slightly chilling thought intrudes: those pretty girls dancing in the aisles, like the superannuated teenager writing these words, are now 50 years old, their dancing days long behind them.

Watching the parade of musicians across Freebody's stage, I was struck last week by how fortunate we were to have been at Newport in the 1950s. The jazz festivals of those years were staged at a time when most of the great musicians of jazz's early years were still alive and flourishing, and when the excitement of bop was still undiminished. With the possible exception of Sidney Bechet -- I can't remember seeing him, but memory may fail me -- every significant living jazz musician played at Newport in those years and most of them, inspired by both the setting and each other, played uncommonly well; to have heard this music, to have seen these men and women as they made it, is a gift beyond measure.

What was it about the setting that elevated the music even above its ordinary brilliance? Perhaps it would have happened anywhere; just bringing jazz out of the city and into the sunshine was, in the 1950s, something of a marvel, for musicians and listeners alike. But Stern's pictures leave no doubt that Newport was the right and only place. It was still an island town then -- the shot of the old Jamestown ferry brought a lump to my throat -- and it was still a small town, uncorrupted by the tourism and development that later changed it. For one long weekend each summer, jazz had this incandescent spot all to itself; given the glorious opportunity, it seized the day.

Proof of which has been available for years on several recordings, most notably those by Duke Ellington and Count Basie. Now at last they are joined by the videocassette of Stern's film. You may get lucky and find it in a music or video store close to home; I got it by mail ($53.95 plus $4 shipping and handling, no credit cards) from Rhapsody Films, P.O. Box 179, New York, N.Y. 10014. If you love jazz, and more to the point if you love jazz in the summer, it would be cheap at twice the price.