In the shorthand version of rock 'n' roll history, one thing happened four decades ago - The Beatles released Sgt. Pepper's Lonely Hearts Club Band, forever changing the face of rock music.
But, as important as Sgt. Pepper's was - and is - it was only one of numerous iconic albums released in 1967, a year that might be the most important in the history of this popular musical form.
The music produced that year still reverberates 40 years later. Some of its albums sound as if they could have been made yesterday.
"I think of it as the dividing line between music that many are embarrassed to look back on and music that almost no one is embarrassed about," says William McKeen of the University of Florida.
"Rock kind of achieves its adulthood in 1967," says McKeen, who teaches a course in the history of rock music. "After that, it could sit at the table with the big boys."
Sgt. Pepper's, The Beatles' magnificent concept album, came out right in the middle of the year, at the beginning of June. No one called them the Mop Tops again.
But it did not arrive on a blank musical canvas. The year featured a panoply of memorable, influential albums produced on both sides of the Atlantic, and on the edge of the Pacific as some of the year's greatest music came out of an amazing artistic ferment in the city of San Francisco.
It was the so-called "Summer of Love" there as the Haight-Ashbury based hippie movement reached the peak of its cultural influence. What that meant musically was that the Bay Area attracted all sorts of musicians from across the country, bringing with them a wide variety of influences and ideas. Together, they produced sounds of a sort never heard before.
Nowhere was this creative cultural clash more evident than when Janis Joplin, fresh in from Texas with her stunning bluesy voice, joined up with a bunch of psychedelic longhairs in Big Brother and the Holding Company, which put out its first album in 1967.
"If rock had a manifest destiny, San Francisco was land's end," McKeen, editor of the anthology Rock 'n' Roll is Here to Stay, says of the reason there was so much great music in that city that year. "If you took the country and turned it on its head and shook out everything weird in those days, they would all end up in San Francisco."
Big Brother came into the San Francisco psychedelic sound from the blues direction. Another group, Jefferson Airplane, arrived from folk music.
Jefferson Airplane had released an album, Jefferson Airplane Takes Off, in 1966, but it was 1967's Surrealistic Pillow, the first to feature vocalist Grace Slick, that put it on the musical map. Again, it took people from across the country to make this music. Slick was from Evanston, Ill.; guitarist Jorma Kaukonen from Washington.
If San Francisco had its native band, it was the Grateful Dead, which also released its first album that year, showing influences as diverse as blues, country, folk, gospel and jug bands. The Dead's eponymous debut marked the beginning of a long strange trip that continues to this day, over a decade after the death of its lead guitarist, Jerry Garcia.
Country Joe and the Fish was another San Francisco group that appeared on the recording scene in 1967 with the very interesting and influential Electric Music for the Mind and Body. Their second album of the year was named for its iconic anti-war anthem, I Feel Like I'm Fixin' to Die.
And the San Francisco area was the setting for 1967's most important concert - the Monterey Pop Festival, a seminal event in rock history. The gathering of musicians - almost all playing for free - might not have been as big as Woodstock, which came along two years later, but musically was probably more influential.
"The classic story about the Montery Pop Festival is that all the record labels came with open checkbooks," says Eric Charry, who teaches the history of rock at Wesleyan University. "They wanted to sign as much talent as they could out of San Franscisco."
It introduced artists like Joplin and Jimi Hendrix, who famously set his guitar on fire. Jefferson Airplane and the Grateful Dead drew wider attention when they played at Monterey. And a crowd of California hippie types was mesmerized by the power of Georgia's Otis Redding and his Memphis-based backing band, Booker T. and the MGs.
Over in England, there was more going on than the Beatles and Sgt. Pepper's. McKeen notes that Roger McGuinn of The Byrds has pointed out that it was really an intercontinental rock war. In 1966, the Beach Boys had released Brian Wilson's masterpiece, Pet Sounds. Sgt. Pepper was in many ways a response by the Beatles. Many other groups continued to ratchet up the pressure.
Much of what was coming out of England was an inventive melding of traditional blues and the new electronic sound.
If you stretch the date a bit and go back to December 1966, you find the release of the first album by Cream, Fresh Cream. But it was really with the group's stunning second album, Disraeli Gears, released in November 1967, that Eric Clapton, Jack Bruce and Ginger Baker redefined the relationship between blues and rock.
Jimi Hendrix was an American, from Seattle. But he went to England to establish himself as a guitar player, feeling kinship with the electric blues styles of players like Clapton and Jeff Beck of The Yardbirds. There Hendrix picked up bassist Noel Redding and drummer Mitch Mitchell to form the Jimi Hendrix Experience.
That group's 1967 album, Are You Experienced?, may well have the most lasting influence of the myriad of amazing albums released that year. On it, Hendrix demonstrated the potential of the electric guitar with a sound no one had ever heard before.
There were other notable British albums of 1967. Mr. Fantasy came out of the new group Traffic with Stevie Winwood's lead vocals. Pink Floyd debuted with Piper At The Gates Of Dawn, their only album with the enigmatic, important Syd Barrett.
The Moody Blues released Days of Future Passed in 1967 Along with that year's debut by Procol Harum, it set the stage for years of dreamy, complex progressive rock.
Back in the United States, San Francisco was far from the only place where rock was stretching its limits in 1967. Down in Los Angeles, the Doors were matching sophisticated keyboard-based music to the odd and powerful charisma of singer/poet Jim Morrison.
The Doors released two albums in 1967, their self-titled debut, with the hit "Light My Fire," and a second, Strange Days, that seemed to sum up the power, potential and pitfalls of the music of that year.
Two other important Los Angeles-based bands were at work in 1967. Buffalo Springfield, with Steven Stills and Neil Young, re- released its debut album - which climbed the charts with the radio hit "There's Something Happening Here" - and put out its second, and best, album, Buffalo Springfield Again.
The Byrds released Younger than Yesterday and, as McKeen points out, recorded most of The Notorious Byrd Brothers, which he calls "one of their finest albums."
The limits were being pushed all over the place. Down in Memphis, a group of high schoolers called the Box Tops, led by 16-year-old Alex Chilton, topped the charts with "The Letter," a quintessential rock song, simple and complicated at the same time.
A legendery soul career also started in Memphis that year as Aretha Franklin released I Never Loved A Man The Way I Love You.
In the East, the Velvet Underground, managed by Andy Warhol, released its first album. Lou Reed and John Cale were in this group, whose influence far exceeded its album sales.
Folk music was heading into new areas with people like Laura Nyro, who made her debut at Monterey; Judy Collins, who released the haunting Wildflowers that year; and Leonard Cohen, whose The Songs of Leonard Cohen came out a few days before 1967 came to an end.
That is not to say that everything musical that came out of 1967 was wonderful. It was the beginning of an age of baroque excess and at times overindulgence was the order of the day.
"Everyone had to make their 1967 album," is the way McKeen puts it. That meant that they had to push the limits and experiment and do strange things, whether it worked or not.
For The Rolling Stones, that album was Their Satanic Majesties Request, which came out in December 1967. It was the Stones' third album of the year after the serviceable Between the Buttons and Flowers.
"All these years later, I know one person who actually likes it," McKeen says of Their Satanic Majesties Request. "Most real Stones fans pretend it never happened."
But McKeen points out that even with this mistake, the excesses of 1967 pushed the Stones into new areas. Their next skein of albums was the best the group ever produced - Beggar's Banquet, Let It Bleed, Sticky Fingers and Exile on Main Street.
"It was the dividing line that marked the beginning of their mature stage," McKeen says of 1967's influence on the Stones.
There were some excesses from which rock music would never recover. Within a few years, the Beatles were broken up and Hendrix, Joplin and Morrison were dead.
McKeen notes that virtually missing from that year was one of the most influential musicians in rock history - Bob Dylan. Ahead of the curves as usual, Dylan made his 1967 album in 1966, Blonde on Blonde. So at the end of '67, he put out John Wesley Harding, a return to a simpler folk sound.
"That was his commentary on the weirdness of 1967 - two guitars, a bass and a drum," McKeen says. Dylan produced that album as his friends in The Band were recording Music from Big Pink, released in 1968, another reaction to the excess of 1967.
Pushing against boundaries is always dangerous, and that is exactly what rock music did in 1967. It moved into areas it had never been before.
And it has never left.
The top 10
Here are writer Michael Hill's choices for the most important rock albums of 1967:
1. Sgt. Pepper's Lonely Hearts Club Band The Beatles
2. Are you Experienced? Jimi Hendrix Experience
3. Disraeli Gears Cream
4. Buffalo Springfield Again Buffalo Springfield
5. Strange Days The Doors
6. Surrealistic Pillow Jefferson Airplane
7. Mr. Fantasy Traffic
8. The Grateful Dead The Grateful Dead
9. Electric Music for the Mind and Body Country Joe and the Fish
10. Velvet Underground and Nico Velvet Underground