LOOK QUICK, IT'S MUSIC VIDEO

The images flash past, fast as an express train. Michael Jackson and Paul McCartney chant ''Say Say Say.'' There are glimpses of snake-oil pitchmen, a canoe, an orphanage, blond Linda McCartney strumming a guitar, Paul shaving. It ends in a whoosh as they all pile into a blue pickup truck. If you blink, you've missed half the story.

It looks a bit like ''Butch Cassidy and the Sundance Kid Meet Alice in Wonderland'' - a larky, pell-mell, sun-dappled pseudo-western. In fact, it's a music video for ''Say Say Say,'' the hit song by Thriller Michael Jackson and Beatle Paul McCartney. As brief as a movie trailer, it cost $325,000 to make and includes 125 quick cuts.

Music videos - of which this is one of the most polished and ambitious - are micro-movies in which quick montages visualize a popular song while the lyrics act as dialogue. Begun by the record companies in the late 1970s as promotional devices for plugging new songs, they rapidly took on a life, creativity, and popularity of their own. Today an entire cable channel, MTV (whose initials stand for ''music television''), devotes 24 hours a day, seven days a week, to music videos. It's the fastest-growing channel in the cable industry.

And that's just the beginning. Already there are signs that videos may alter or even transform cable television, broadcast TV, motion pictures, and the record industry - as well as the worlds of composing, performing, and advertising - in much the same way that ''talkies'' rocked the silent-movie industry.

Music is increasingly written with visuals in mind, and performers are chosen for visual potential: Now that a once-obscure English group, Duran Duran, has proved it can rise to the top of the charts through heavy play on MTV, the entertainment industry is sizzling with possibilities. Nearly 200 TV stations across the country broadcast music-video programs.

Already Hollywood moguls have begun releasing music-video feature films. Network TV barons are discussing fall TV pilots ''enhanced'' by music videos. Radio stations and record companies are thriving on the increase in sales generated by music video. Even TV commercials are under the influence: It is difficult to tell a ''Candies'' shoe commercial from one of the less ambitious music videos.

What is it about music videos that sparks both viewers and the entertainment industry? The best of music videos are like popcorn: You can't watch just one without wanting to try another. Given the visual and musical fascination of videos, it's possible to drop a couple of hours in front of the tube without realizing it - hooked by the beat of the music, the vivid and quickly shifting images, the unexpected new sight and sound just beyond the next video bend. The most stunning of the videos bring you back again and again to watch: David Bowie's romantic ''China Girl'' and ''Let's Dance''; the dance among massed candelabra in ''Wrapped Around Your Finger,'' by The Police; Eurythmics' surrealistic ''Sweet Dreams'' and ''Here Comes the Rain Again''; the prancing glamour of Lionel Ritchie's ''Running With the Night''; the pulsing Americana of John Cougar Mellencamp's ''Pink Houses''; the revved-up satire of Thomas Dolby's ''Hyperactive''; and the zany bounce of Cyndi Lauper's ''Girls Just Want to Have Fun.'' Unpredictable, lively, innovative, they are further from conventional TV and closer to the dreams on which Ingmar Bergman once said movies are based.

Many videos, in fact, have that dreamlike (or, in the case of violent videos, nightmarish) quality. Short bursts of vivid images, unconnected by dialogue or structured plot, they read like memos from the imagination. Relying on rapid-fire cutting and experimental techniques, they can also be video crazy quilts. Borrowing footage from old movies, newsreels, and cartoons, they also incorporate animation techniques - as well as the surrealistic effects of artists ranging from Dali to Magritte. They pummel the viewer with startling, quick images - some evocative and romantic, some mysterious and quirky, some funny and wild. They also surprise the eye inured to decades of cloned TV sitcoms, game shows, soap operas, and cop series.

There is, too, the darker side of some music videos. The gratuitous violence and eroticism of performers like England's Billy Idol, for instance: His work has the nightmare quality of a painting by Hieronymous Bosch. One video includes scenes of sadomasochistic bondage, followed by the apparent sledgehammer-murder-to-music of a woman victim. The emphasis on homosexuality or androgyny in some hit video acts - like those of Boy George of Culture Club - also raises troubling social questions for impressionable younger viewers.

Dr. Thomas Radecki, head of the National Coalition on Television Violence (NCTV), says the group's monitoring of MTV indicates that half of its videos are violent in lyrics or visuals. But he adds that ''in any hour on MTV, maybe only two of the videos will be high in violence . . . you don't see massive amounts of violence, like (the movie) ''Texas Chain-Saw Massacre.''

NCTV has put together a ''violence clip'' with scenes from 10 of the most violent videos - from Michael Jackson's ''Thriller'' (27 acts of violence) to the Rolling Stones' guerrilla war video, ''Under Cover of the Night.'' Dr. Radecki concludes that MTV is not any more violent than some of the network television series.

The music videos that are the subject of such speculation and controversy got their big start in the early '80s, after a 10 percent plunge in record and tape sales in 1979 from an all-time high of 726 million. Using the four-minute music videos begun as promos for a flagging industry, TV began eclipsing radio as a sales medium - and made stars out of previously obscure new-wave, punk, and experimental groups. Sales soared, up to an estimated $3.77 billion last year.

The jazzy catalyst for music-video success has unquestionably been MTV: Duran Duran sold 10 million albums after heavy MTV exposure, and the race was on. MTV, the Xanadu of rock and pop, is an anything-but-stately pleasure dome of sound. It devotes 24 hours a day to playing music videos - as well as news, contests, promotions, concerts, and interviews with mellow ''VJs'' (''video jockeys'') like Martha Quinn, whose studio set resembles a loft apartment.

MTV, owned by Warner Amex Satellite Entertainment Company, began in 1982 with 300 cable outlets reaching 2.5 million homes. Today, says MTV president Jack Schneider, it reaches 20 to 22 million homes. He predicts an 80 percent saturation of the TV market by 1989. Mr. Schneider, a former CBS network president, says music videos are ''a new art form.''

''We have taken preexisting forms, motion picture and records,'' he says, ''and married them to the television industry . . . carrying the old, preexisting media, examining what they do and adapting it.''

Now, however, the old existing media, like broadcast TV, are doing some adapting of their own. Spokesmen for the networks confirm they have pilots in the works for TV series that ''adapt'' music-video techniques and ''enhance'' the programs. NBC lists ''The Dreamers,'' ''High School Confidential,'' ''HeartBeat,'' and even ''Miami Vice'' (about a vice squad presumably engaged in song and dance). CBS has ''Dreams'' (from Jon Peters of ''Flashdance'') and ''Hot Stuff,'' about a quartet of dancers. So far, ABC (the only network without a record company) has introduced videos only in a soap, ''General Hospital.'' NBC's vice-president for series development, Jeff Saganski, says he doubts that music-video programs will air ever on prime time. But ''the network is experimenting,'' he adds, ''to see what their appeal is.''

Will the experiment work? Dick Ebersol, executive producer of ''Friday Night Videos'' on NBC, suggests that using music-video techniques in series ''is a lot of hype . . . so they can say in a press release they have prime-time shows (with music videos) . . . as a way to hype the shows to the ad industry.''

He believes younger viewers are bored by the static visuals of today's TV series and turn away from them to music videos, where ''in four minutes you can see 100 to 300 images; the eye is occupied.'' This new form, he adds, ''is going to have its greatest impact in the late '80s, when a generation that's grown up with music videos will demand a change in the visual quality of TV.''

That change is already evident in movies, where the first music-video feature films, ''Flashdance'' and ''Footloose,'' have been so wildly successful at the box office that a blitz of vid-films is on the way. Among them are Warner's rock video movie ''Vision Quest'' and the just-released ''Hard to Hold,'' starring Rick Springfield. Many of the top video directors, like Bob Giraldi, Steve Barron, and John Mulcany, are making feature films - while established movie directors like Bob Rafelson and Jon (''Thriller'') Landis are shooting videos as an alternative to the big-budget Hollywood films.

And many movies, from ''Against All Odds'' to ''Yentl,'' are heavily advertised with promos that look like music videos - and often are. As a result, the line between art and advertising is increasingly blurred. The hit video ''Maniac,'' by Irene Cara, is really a montage of dance clips from ''Flashdance'' backed by the song, while the title number of Kenny Loggins's ''Footloose,'' a teen dance scene, is pinched directly from the movie reel for a music video.

The result of this sudden deluge on the entertainment world is that music videos have become a light industry in themselves. At network affiliates like CBS's WDVM in Washington, they are considered a bonanza of popular programming at low cost. Wally Ashby, producer of the station's ''Music Video Connection,'' points to the variety of free ''compilation reels'' (collections of videos provided by record companies) and to industry literature.

Michael Rowan, president of Creative Video Consulting's C.V.C. Report, predicts that the whole picture for music videos will change radically as record companies begin charging programmers for videos. CBS Records spokesman Jerry Durkin concurs. ''Eventually all outlets are going to pay a fee based on the size of the area they cover,'' he says. (''Friday Night Videos'' insists on paying a fee.)

So far, the trend has been limited to videos for popular music - pop, rock, rhythm and blues, soul, and country - shown on stations across the nation. But some observers are wondering about the potential for serious-music videos - excerpts from Mozart's ''Magic Flute,'' for example, with montages of Met singers and Chagall's dazzling sets.

That may not be far away: Walt Disney's ''Fantasia,'' which is set to serious music, has enjoyed a recent revival. As an 11-year-old said on seeing the movie for the first time: ''Was this the first music video?''