That great, sick punchline is the message that springs out of the boxed set Elvis: Walk a Mile in My Shoes, The Essential '70s Masters (RCA). To listen to these five CDs is to hear Elvis struggling to escape from a shrinking closet, trying to wriggle free of the mediocre material he settled for, the tossed-off quality of his singing that came from no longer having to prove anything. And now, 18 years after Elvis's death, these performances have something else to struggle against: the image of Elvis as a bloated, pill-popping joke rattling around his tacky Memphis mansion, half-crazed from fame and pharmaceuticals and Southern-fried cooking.

This is the image that necrologist Albert Goldman served up with such glee - the King as Burger King. And as a pop icon, it arguably rivals the image of Elvis as the sleek, young, beautiful rebel. Too many Elvis worshippers have already expended enough energy denying the pills, the weight gain, the craziness. They seem unable to see (as the people who sneer at Elvis are unable to understand) the triumph of his talent alongside the horror of the way he squandered it. But there's also no denying that the image of the fat, decaying Elvis has made it possible for people who never cared about him in the first place to dismiss him. And that image has made it easy to assume that the music he made in the last years of his life was worthless.

Walk a Mile in My Shoes is the hard proof that those claims are going to have to grapple with from now on. That's not to say it doesn't present its own set of problems. Except for 1972's "Burning Love" (one of Elvis's three or four greatest singles), the music in this set doesn't offer the excitement of his '50s performances or the best of his '60s work. There's only one recording from the last year of Elvis's life (a concert version of "Unchained Melody"), and especially on some later numbers you're aware that his voice has lowered and thickened. The material is uneven; much of the first two discs (the A and B sides of his '70s singles) is, frankly, dreck. His emotional commitment varies from song to song, but not one performance sounds as if it were being given by the slurring, self-parodying zombie the later Elvis was supposed to be.

There's a scarifying and heartbreaking moment from a concert filmed just six weeks before his death (and broadcast posthumously on CBS). Facing the crowd, bleary-eyed and bloated, Elvis begins, "If you think I'm nervous . . ." And there's an almost unbearable pause before he says, "You're right." He seems to be asking the audience if they still want him as he is. And then he breaks into "I Can't Help Falling in Love with You." It's not perfect, it's a little slow, and still you hear a voice capable of stirring up longings and dreams you may have thought you abandoned - and you try to put it together with the unsteady man it's emerging from. That was the curse of Elvis, turning into a caricature of himself and not losing his voice.

There are hints of the young, impudent Elvis on Walk a Mile in My Shoes. On "Cindy, Cindy," he sings, "Wish I was an apple/Dangling from a tree/And every time you passed me by/You'd take a bite of me" with a salacious sneer in his voice that's miles away from the good-natured sing-along Ricky Nelson, Dean Martin, and Walter Brennan performed in Howard Hawks's wonderful Rio Bravo.

But it's safe to say, I think, that not even the young Elvis was capable of the giddy, terrifying depths of "Burning Love." Let Mick Jagger prance around and proclaim himself Lucifer. (Oooh, I'm so scared!) Let Jerry Lee Lewis worry about the hellfire he thought he was going to burn in for singing rock and roll. Elvis sings as a man roasting in the fires of damnation - except that he likes it. His voice is an echo, as if it were coming from the deepest circle of hell, the sound of it distorted by towering walls of flame much the same way heat makes the horizon look wavy. Throughout the song, images of torture keep turning into images of ecstasy ("It's comin' closer/The flames are now lickin' my body"; "I just might turn into smoke/But I feel fine"). We're listening to some Dionysian rite where self-destruction becomes self-realization. Instead of turning into smoke, Elvis seems to absorb the heat into himself until, by the end, he's getting stronger with each repetition of "I'm just a hunka hunka burnin' love," spitting out each syllable as if his voice were a flame thrower obliterating everything in its path.

But for the most part, the music on Walk a Mile in My Shoes is made by a man who knows he's no longer a teenager. The live version of "Heartbreak Hotel" that's included is tossed off, an obligation. The rock and roll Elvis does here isn't teen music. It either has a rootsier feel ("Proud Mary," "Polk Salad Annie") or is rooted in the sort of emotional contingencies teen music doesn't admit ("Suspicious Minds," or his great version of Billy Swan's rockabilly hit "I Can Help"). With the exception of John Lennon, I can't think of another major rock-and-roll figure whose work took into account his age as Elvis's does here.

In 1971, when Elvis accepted the Jaycees award for being one of the Ten Outstanding Young Men of the Nation, he said, "I learned very early in life that `Without a song, the day would never end; without a song, a man ain't got a friend; without a song, the road would never bend - without a song.' So I keep singing a song." Walk a Mile in My Shoes makes a good case that Elvis, who was so shy, so shambling in interviews, could fully express his emotions only through music. What I mean by that isn't just that he uses some songs transparently as autobiography, as he uses the gospel weeper "You Gave Me a Mountain" to tell the story of the break-up of his marriage. I mean that he turns to songs, all different kinds of songs, to see what they can reveal to him about himself. Some of the best moments here are rehearsal tapes where Elvis keeps a number going for minutes at a time, pushing it, testing it to see what it will yield up, or else just sings a snatch (as he does with "Lady Madonna" and "I Shall Be Released") that gets to the emotional essence of the song.

The best moments of Walk a Mile in My Shoes have the warmth, the generosity of feeling, and the genius of phrasing that characterize the work of great American singers like Sinatra, Ray Charles, Charlie Rich, and George Jones. But Elvis's heavier reliance on country, which, unlike rock, is music about loss and compromise, stirs up feelings that are perhaps irreconcilable. It's an odd sensation to hear him admit to the possibility of compromise, even as you know that insisting on hearing him only as the young man who had everything in his grasp is to deny him the chance to present himself to us as a human being, and to enter the queasy realm of worshippers blind to the fact that his greatness and his failure come from his humanity.

There are two numbers on Walk a Mile in My Shoes in which Elvis tries to address the burden of being Elvis, and they couldn't be more different from each other. The set ends with the 1970 rehearsal version of "Stranger in My Own Home Town," which may be the most shocking Elvis recording I've ever heard. It's certainly his toughest blues. The performance seethes with resentment at the way fame has imprisoned him ("My home town won't accept me, I just don't feel welcome here no more"), and yet he'll be damned if he'd give any of it up. When he sings, "I'm goin' back down home to Memphis, start drivin' that damn truck agin," you can feel how much he hated being nobody. It's the sound of a man who doesn't know which way to turn, except to music. So he burrows deeper into the song, getting harsher the further he goes, keeping the song going so he has a place to put the bitterness roiling around inside him.

It's hard not to feel implicated in the anger of "Stranger in My Own Home Town." Elvis's 1976 version of "Danny Boy" is the sound of a man who's tried to make peace with himself, and with us. If you're wondering what's left to do with an overworked tearjerker like "Danny Boy," I can say that this version, accompanied only by piano and featuring Elvis in magnificent voice, is one of the most beautiful and the saddest things I've ever heard.

Elvis could easily identify with the story of a boy who travels far from his home. Although he never got farther from Tupelo than Memphis, metaphorically he'd gone light years. "Danny Boy" is sung by someone (mother, father, lover) the boy is leaving behind. Elvis turns it into an elegy for himself, as if the boy who's leaving were his own younger self. "The summer's gone . . . But I'll be here in sunshine or in shadow," he sings, and it sounds like a reckoning up, an admission that he may not have always been as young and beautiful as we wanted him to be, but at least he was always there, and his failures and triumphs were his alone. The final ethereal notes that follow the line "I shall rest in peace until you come to me," are like a spirit taking leave of a body. This overlooked number is the very thing that Elvis's death seemed to rob us of: an honest, loving goodbye.