Ten years after Elvis strolled into Sun Records in Memphis, the music he helped create — rock 'n' roll — looked like a bloated corpse, its raw energy replaced by vapid dullness.

Elvis had gone Hollywood; Buddy Holly had died, and it was hard to determine which career move was worse. The musical landscape was bleak, peopled by the likes of Frankie Avalon, Bobby Rydell and Pat Boone. The great soul artists enlivened popular music with their transcendent blend of gospel and blues, but when it came to guitar-driven rock 'n' roll, the music was on life support, ready for burial in a pile of heartthrob rubbish.

Then, on the night of Feb. 9, 1964, a quartet from Liverpool appeared on "The Ed Sullivan Show."

"Ladies and gentlemen, the Beatles!" With those five words, Sullivan launched the rebirth of the music that had ignited the nation 10 years earlier. And nothing symbolized the revolution more dramatically than the contrast between the host and his guests. There was Sullivan, stiff and stern as an undertaker. And there were the Beatles, vibrant and subversive, their music as daring as their haircuts.

Ah, their music. Sullivan introduced the group, and the world would never be the same. The Beatles performed two sets, beginning with "All My Loving," a joyous celebration of teenage love — a love reciprocated by the studio audience, which was mostly adolescent, mostly female and mostly screaming. The girls were not alone. Picture a giant living room, encompassing every state in the union. More than 73 million Americans tuned into the show — a staggering 38.4 percent of the U.S. population in 1964.

With millions viewing at home, the Beatles created a delicious tension with the count-in to their first song — "One, two, three, four!" And when they reached "four," it started, the mayhem with a melody that captivated the nation and the world.

Holding our hands, the Beatles escorted us into the future, a grand reason to mark the 50th anniversary of their appearance on Sullivan's program. "They provided a variety of songs like no other group at the time — story songs, love songs, lessons in existentialist thought ['Eleanor Rigby'], psychedelic rock, etc.," Mike Kearl, a sociology professor at Trinity University in San Antonio, said. "Theirs were songs one could generally sing along with — from beginning to end. And like Dylan, they had lyrics worth listening to."

"Their music was like this perfect distillation of attempts at high art and innovation into a three-minute pop song," Steve Alejandro, the co-manager of Hogwild Records & Tapes in San Antonio, said. "The band certainly became a measuring stick. Since the Beatles demise, nearly every band has been judged against or compared to the Beatles. Any time a band releases an LP that is a little off their usual musical path, it's compared to 'The White Album.' Think of Fleetwood Mac's 'Tusk' or The Clash's 'Sandinista!' or Radiohead's 'OK Computer.' "

The appearance on "The Ed Sullivan Show" came almost four months after the assassination of President John F. Kennedy, and it did more than help the nation heal, Kearl said. "With their appearance, the period of mourning was to come to an informal close," he said.

The performance may have been in 1964, but the country seemed to defy the calendar. America appeared stuck in the 1950s, both musically and socially. It was the kind of world depicted in the popular AMC series "Mad Men" — rigid, boring, button-down, a world of crew cuts, skinny ties and instant coffee. A year earlier, "The Beverly Hillbillies" and "My Favorite Martian" drew top ratings on TV, while "The Nutty Professor" and "Fun in Acapulco" (the latest dreadful Elvis movie) attracted huge audiences to theaters. The wasteland seemed even starker on the radio, with hits that included "Blue Velvet," "Hey, Paula" and "Puff the Magic Dragon."

It was a dreary, enervating landscape, and it begged for a revolution. John, Paul, George and Ringo were part of the upheaval — musically, culturally, socially. But did they trigger it? Or were they caught in the same social current that was sweeping everyone else along, a current as irresistible as the music, leading us to a generation that seemed hooked on pot, protests and psychedelia?

"The Beatles were certainly part of a cultural zeitgeist, in part shaped by and in part shaping the phenomenon," Kearl said. "The '60s [were] a time when the baby boom cohort became a generation, a self-conscious agent of social change."

The Beatles were so influential that they inspired people in the Soviet Union. "We knew their songs by heart," Pavel Palazchenko, the Soviet interpreter for Mikhail Gorbachev, once told a writer. "They helped us create a world of our own, a world different from the dull and senseless ideological liturgy that increasingly reminded one of Stalinism. … The Beatles were our quiet way of rejecting 'the system' while conforming to most of its demands."

Six years after the "Ed Sullivan" appearance, "Let It Be," their last released album, was intended as a retrenchment, a return to their musical roots. It was anything but. "Let It Be," like all their albums, was breathtakingly diverse, encompassing soul, folk, rock and, according to one critic, "cosmic" ballads. It represented an exquisite journey into the future of rock 'n' roll. Despite a tinge of sadness and regret, the album spoke of possibilities.

And yet, it was over. The Beatles, as a group, had nothing more to offer. What they did give us, however, will last as long as vinyl, CDs and dreams last. From "With the Beatles" on, each new album built on the freshness and innovation of the previous recording. They lit the way to the future, while the Avalons, Rydells and Boones became part of the roadside debris, their lack of talent exposed by the Beatles and other artists, including Bob Dylan and the Rolling Stones. And it all started, at least for Americans, on that night 50 years ago.

"The Beatles swept away Pat Boone, the Kingston Trio, doo-wop, and all the other twaddle in about 36 hours," author Joe Queenan writes in "The Beatles Are Here," a newly published collection of essays on the Beatles.

Allen Ginsberg, the great American poet, went a step further, saying that the Beatles had turned their hometown of Liverpool into a universal "center of consciousness."

"I think a good way to assay a band's importance is to listen to their first LP and then their last LP," Alejandro said. "Do they sound like the same band? Certainly there are bands who have not changed much from first to last, and they remain important and great bands, but there is something to be said of a band that changes and adapts the way the Beatles did."

It is that growth that makes the Beatles vital to a new generation. "From a fan's perspective it's phenomenal," he said. "It's as if you are growing with them. I certainly believe that in 50 years, people will be celebrating the 100th anniversary of the Beatles first LP and their first appearance on American television."