The underworld of art, it seems, is just as sleazy as any other underworld. As recorded by ABC News, it is inhabited by Mafia-like double-dealers. That's the message one gets from an almost totally ''reenacted'' documentary presented by ABC News's often innovative-or-bust ''Closeup'' series: Alias A. John Blake (ABC, Saturday, 10-11 p.m., check local listings). The documentary points a lot of ambiguous fingers in trying to explain the $1 billion-a-year (who really knows?) world of stolen-art dealings.
Correspondents Pierre Salinger and John Fielding, with the help of a fine performance by a London newspaper reporter named Peter Watson, trace the nefarious dealings of a supposed crooked art purchaser as he arranges to buy a stolen Caravaggio, a del Sarto, and other purloined paintings.
The ''crooked art purchaser'' is reporter Watson, also known as A.John Blake. And in the course of his scheming, he presents viewers with a detailed blueprint on how to arrange for a new identity.
Almost as an afterthought, this ''ABC Closeup'' throws in some interesting footage about grave robbers in Italy and Colombia. Since most of the other parts of the film have been ''reenacted'' by the players involved, one wonders how authentic the ''actual'' grave robbing scenes are.
Some basic matters are touched on too lightly in this docu-reenactment. They stir up interesting unanswered questions. How were the privately owned masterpieces acquired by the wealthy in the first place? Do reputable art dealers really wish to maintain the status quo in regard to vagueness of the source of major masterpieces?
''It took almost two centuries,'' says Salinger on the show, ''for the Greeks to get angry about the fact that part of the historic Parthenon is in the British Museum.'' But are we being fair to the British when we do not consider the alternatives if the famous Elgin Marbles had not been ''rescued'' from the Parthenon?
Yet ''Alias'' does not want you to forget that it wants to be a respectable and responsible film. Mr. Salinger intones at the conclusion: ''As our investigation has shown (has it, really?), the international trade in stolen art is vaster than is generally understood, and second only in value to the smuggling of drugs. But drugs are more dramatic; they visibly destroy and kill people. The slow and inexorable rape of a nation's culture is harder to perceive and takes far longer to understand.
''This is perhaps one explanation for the lack of outrage and concern . . . in government and the general public. . . . Only with heightened international consciousness can this underground attack on national heritages be stopped. Otherwise, grave robbers will finish their pillage of the art treasures of Italy and South America. . . .''
Although ''Alias A. John Blake'' has dug up a fascinating topic, it creates all sorts of questions of morality as well as of proprietorship. Maybe one day soon we'll get a more balanced picture of the problem from experts, even though it might mean talking heads instead of melodramatic reenactments. Pop goes the orchestra
The Boston Pops sound may be America's quintessential populist music form.
While country music, jazz, and rock represent specific elements in popular culture, the Boston Pops Orchestra sound combines many elements, presenting them in forms enjoyable to a wide range of listeners - although purists of both the classical and pop variety often object.
But ordinary people who like to listen to pleasurable sounds can appreciate fully the unpretentious pop, light classical, movie, and Broadway music of the beloved Pops.
All of which is a prelude to a preview of the premiere concert in the 14th season of Evening at Pops (PBS, beginning this Sunday, 8-9 p.m., check local listings for premiere and repeats).
If Pops is the true populist orchestra, then this ''John Williams Special'' is the true populist music show. In a bold stroke devoid of phony modesty, music director John Williams - a composer, conductor, and musician in his own right - showcases himself. He conducts excerpts from his Academy Award-winning score for ''E.T.,'' plays the harpsichord in a rousing rendition of Vivaldi's ''Concerto for Four Violins and Orchestra,'' and skillfully conducts Dukas's ''The Sorcerer's Apprentice'' (which nonclassicists may remember from the Disney film ''Fantasia'').
As a glorious climax, Williams conducts the orchestra and the Tanglewood Festival Chorus in a rendition of his own frankly flag-waving song, ''America, the Dream Goes On,'' while the video camera meanders through the Norman Rockwell Museum in the Old Corner House in Stockbridge, Mass. Now, that's American!
It's a good old show - a harbinger of fine pop things to come on the series, which continues on Sundays through Aug. 21. Next week there will be Steve Lawrence and Eydie Gorme in a salute to Irving Berlin. Future shows will feature Judy Collins, Nell Carter, Marvin Hamlisch, Bernadette Peters, and Peter, Paul and Mary.
Despite the seeming determination of WGBH in Boston not to be at all condescending in its presentation of this series of concerts, the fact is that it is not being simulcast on FM radio, which would otherwise allow viewers to evade the tinny sound of most TV speakers. Major ''classical'' music events usually rate that kind of treatment. Why shouldn't the Pops?