New Technology Is Pushing the Process of Rediscovery : Music: The improved sound and picture quality of laser discs gives vintage rock movies a new kick.

One of the unexpected side effects of the compact disc revolution has been to make old albums seem fresh again.

Even friends in the record business who almost never listen to old vinyl albums because they are so busy keeping up with new releases are making time to play old favorites when they arrive on CD.

“There is a definite rediscovery process at work,” said Pete Howard, publisher of ICE, a Santa Monica-based CD newsletter. “If the album has been remastered correctly, there is a strong possibility that you will hear instruments and music that you hadn’t heard before on the vinyl record or cassette. So, it’s a definite rebirth of some kind.”

The process now appears to be repeating itself with laser discs. Though most key, music-related films have been available on videocassette for years, the improved sound and picture quality of laser discs gives the films an immediacy that makes you you feel as if you are seeing them in a new light.

The fascinating thing about seeing some of these films for the first time in a decade or more is how they stand up against your memory.

Prince’s “Purple Rain,” for instance, was hailed by some critics in 1984 as the best rock movie ever--a work that stepped far beyond the exploitation nature of most films in the genre. Yet it struck others as little more than an update of the early Elvis Presley movies--say, “Jailhouse Rock.”

So how do the films compare today? “Purple Rain” and “Jailhouse Rock” are two of the four vintage films included in this look at music-related laser discs. Discs are rated on a scale of one (poor) to five (a classic).

*** 1/2 “Jailhouse Rock” (MGM/UA). The makers of this 1957 film knew what they were selling. Elvis enters the movie within 11 seconds and the camera rarely leaves him in this predictable tale of the rise and temporary fall of a young rebel in the music business.

The surprise, in view of the hapless nature of most of Elvis’ later films, is how Presley exhibits fleeting signs of genuine acting talent. He was just 22 when he made “Jailhouse Rock” and was clearly over his head as the lead in a film, but he shows at times the brooding intensity and charisma that he conveyed on stage. With discipline and guidance, he may well have evolved into the actor that he often said was his unrealized goal.

*** “Purple Rain” (Warner Home Video)--”Purple Rain” not only is far from a masterpiece, but it’s also debatable whether it is even as good as “Jailhouse Rock.” The Prince movie’s greater ambition is more a sign of rock’s increased status and power in the entertainment world in the ‘80s than a sign of Prince’s skills as a filmmaker. Where Elvis was an actor going through a part outlined by Hollywood in “Jailhouse Rock,” Prince had or shared control of virtually every aspect of this 1984 release.

Yet the story--another misunderstood Kid, searching for identity through music--is ultimately as limited as that of “Jailhouse Rock,” and Prince, for all his presence on stage, turns out to be a far weaker actor than Elvis. What gives the movie its sizzle is the concert footage.

*** 1/2 “Performance” (Warner Home Video)--Though Mick Jagger, in a teasing role as a decadent ex-rock star, was the selling point of this dark, unsettling 1970 film, “Performance” was far too ambitious to be considered simply a rock exploitation movie. In fact, Jagger isn’t even in the film for the first 40 minutes. The opening sequence is a taut, brutal chronicle of a minor hoodlum (James Fox) who enjoys terrorizing shakedown victims until he becomes a target himself.

Looking for a place to hide, Fox stumbles into Jagger’s bizarre world and becomes so caught up in the madness of drugs, sex and potential violence that he becomes as helpless as the victims he once tormented. A powerful but also confusing and indulgent film.

** 1/2 “Joe Cocker/Mad Dogs & Englishmen” (Pioneer Artists)--Filmed a year after Woodstock, this concert documentary exudes some of the lingering flower-power ambience of the period, but the real treat is seeing Joe Cocker at his prime. Assisted by musical director/guru Leon Russell, the passionate British blues-rocker was such an engulfing performer that it’s not at all unreasonable to think of him as the male Janis Joplin of the early ‘70s.

** 1/2 “Public Enemy: Fight the Power Live” (CMV Enterprises/Image)--A somewhat scattered yet still useful introduction to rap’s most important group, combining concert footage and video clips of material taken mostly from the group’s first two albums.