Most of the Elvis that the public will encounter in this demicentennial month is familiar Elvis: freeze-dried in '50s kinescopes, clipped from his 33 movies, sweating and smiling under the glare of press conference lighting. He will be the Elvis Presley of our fantasies, and probably his.

HBO's "Elvis: One Night With You" is something else again. It captures Elvis at a pivotal moment in his career. In June of 1968, Elvis was at one of the lowest ebbs in his career. At the behest of his manager, Col. Tom Parker, he had removed himself from live performances in 1960, channeling all his energies into an increasingly vapid series of Hollywood films ("my travelogues," he called them) and sound-track albums.

Staggered both by the British Invasion in the early '60s and by the West Coast flowering later in the decade, Presley's position as rock catalyst and pop icon was anything but secure. Something was needed, and Parker, who had been rejecting television proposals since Elvis' post-Army guest spot on a Frank Sinatra show in 1960, thought it should be an Elvis Christmas special, with Elvis singing carols in a tuxedo. Luckily, Parker didn't have his way.

The reason was producer Steve Binder. Binder was already something of a maverick. He'd done the seminal "T.A.M.I. Show" as well as a 1967 special that had broken a television taboo when Harry Belafonte touched Petula Clark during a song. He was also a dedicated fan who remembered the original Presley fire and sought a way to rekindle it by returning Presley to his rock 'n' roll persona. It would be, Binder hoped, Presley's moment of truth.

Much of what eventually became the "Singer Special" (named after the sponsoring sewing machine company) consisted of inspired spins on Presleyana, particularly the opening sequence with 100 shadowy Guitar Men recalling "Jailhouse Rock," and throughout Elvis looked simply marvelous. He'd gone to Hawaii and worked out, lost a lot of weight; when he stepped on stage, he'd never looked better (nor would he look as good again). Presley was lean and sinewy, the hillbilly cat dressed to the nines in Bill Belew's mind-boggling wardrobe (Belew would become Presley's costumer-for-life after this program). More importantly, Presley seemed to have rediscovered the inborn sexuality central to his original stance. The show restored him as a genuine rock 'n' roller and was the first step back to the concert stage.

But what most fans recall from the "Singer Special" is the 10-minute segment in which Elvis appeared informally on a small stage with his original guitarist and drummer (Scotty Moore and D.J. Fontana) and reminisced about, and thus re-created, his early career. Thrown back to the simplicity of the Sun recording sessions that had originally defined him, Presley reached into himself at the same moment that the audience confirmed him. It was a transcendent moment, not just for television but for Presley. But it was not what Parker or Singer, or NBC for that matter, was looking for. As a result, the greatest portion of two hours of film shot before two small audiences sat in the NBC vaults for 16 years. Now an uncut, unedited version of the first of the shows will be seen on HBO, starting tonight at 8, with repetitions on Jan. 8, 11, 14, 17, 20 and 23.

Presley was, not surprisingly, apprehensive about this particular segment, one that would put him in close contact with a live audience for the first time in almost nine years. Asked what he felt by Binder, he replied, "Sheer terror." When the time came for him to step onto the 15-foot-square platform (Binder envisioned it as a boxing ring), Presley tried a last-minute back-out. But he went on and though his first words were "Well, good night," and his first action was a bolt, he stayed to give "an idea of how I started out 14 years ago and our sound back then." Later Presley added, "I'd like to talk a little about my music. Very little." And that was fine, too, because he'd proved he could reach back to his original inspiration.

That was something important for Presley to remember, but you could sense the pull of his subsequent pop persona. He starts off with "That's All Right, Mama" (introducing it as "That's All Right, Little Mama"), the key a little too high, but the passion intact, the vocal charge as tough as the black leather suit he's wearing. "We got out of that one," Scotty Moore sighs at the end, and that does seem to be Presley's approach on several songs. He moves through the stages of his early career, from the raucous "Heartbreak Hotel," "Blue Suede Shoes" and "One Night (With You)" to an elegiac "Are You Lonesome Tonight" and a flaccid "Memories" that suffers from returning Elvis to the studio band. "Baby What You Want Me to Do," with Elvis switching to electric guitar, crops up three times, as if it's not just a song, but a vital question at this juncture in Presley's career.

The rapport between Elvis and his longtime musicians is genuine, and early on he seems to forget the 200-member audience. That allows for the kind of after-hours intimacy and spontaneity that Binder had first spotted during rehearsals. It is a totally new aspect of Elvis, a revelation of the man behind the myth.

But even as he finds his voice, Presley questions the process. He clowns around (his very natural, quick, and sometimes self-deprecating sense of humor comes through again and again), forgets lyrics, muffs transitions, demands cajoling on stories. It's as if he's putting himself on, which was a subtext to his whole career. Still, Presley seems to gain confidence as the show goes on. He reportedly went to his dressing room and wept afterward.

"Elvis: One Night With You" is drawn from the first of two shows shot for the "Singer Special," and one hopes HBO will show the second hour. In any case, anyone who has ever wondered about Elvis' magnetism will come away confirmed by this performance. What's most interesting, perhaps, is how contemporary Elvis looks and sounds even now: "One Night" may have been a 1968 revival of '50s music, but it's also a timeless moment, which the best music, and the best television, should always be.