"Thick," as its devotees have always called it, was a single song that filled both sides of a 44-minute vinyl album. Its sometimes provocative, sometimes abstract lyrics about such topics as global and generational conflict and people's expectations of life were reportedly penned not by Tull's flute-wielding frontman, but by one Gerald Bostock, a 10-year-old resident of the quintessentially British village of St. Cleve.
Musically, "Thick" was a textbook example of early-1970s progressive rock, roiling with tricky time changes and sonic blueprints that hopscotched between pastoral acoustic passages and belching riff-rock that wouldn't have been out of place on Led Zeppelin or Deep Purple albums of the era.
Anderson may have tried to a pull a fast one with "Thick As A Brick," but the joke turned out to be on him. His attempt to mock the "prog-rock" aesthetic became the only Tull LP to reach the top of the Billboard album chart in the group's 40-year-plus history. It also established Tull as one of the giants of the age (they're one of just a handful of acts who have sold out Madison Square Garden for five successive nights).
Which brings us to 2012 and the recent release of "Thick As A Brick 2" (EMI), a sequel - and update - of the original piece. On Saturday, Anderson will be performing both "Thick" albums at Caesars Atlantic City.
Anderson offered that the first "Thick" - which, he said, surveyed "the [journey] from childhood to manhood" - was "a parody, a spoof, a bit of a send-up of [the era's progressive-rock conventions], whereas 'TAAB 2' is a bit more cynical, more grown-up, a lot more world-weary."
"While ["TAAB 2"] has its upbeat and humorous moments, it also is touching upon some difficult subjects - the failure of parents to deal with children who are going through gender-identity crises, and perhaps who drive their children out of their homes and into the clutches of the underbelly of society."
He added that other subjects on the new album include "the futility of war, the excesses of the archvillain investment bankers in the recent economic downturn of 2008. There are things I wanted to make different. I wanted to have a darker side to it."
Despite the differences, the two works do share thematic and musical bonds.
"There are some parallels in that 40-year period, for instance . . . homelessness, drug-taking, the sex trade, evangelism, themes of capitalism. And, perhaps, the apparent futility of war," Anderson said.
"In 1972, we were just a year away from the pullout of American troops in Vietnam. The net result, of course, was the Vietnamese swept right in and installed their Soviet-style socialist republic which endures to this day. Here we are in 2012, a year away from the drawdown of troops from Afghanistan, and the Taliban are waiting in the wings to ride back into town on there trusty steeds and subject women and children to a life of extremist Islamic culture, tribal culture.
"There is this way in which some things unfortunately tend to repeat themselves. So I thought there was a lot of material there that could be built upon."
Anderson explained that he conjured "15 possible scenarios" of how the fictional Gerald Bostock's life could have unfolded. "I realized that rather than pick one, maybe it would be a good plan to pick five and have a look at those [instances] pivotal in his life, and our lives, where you're forced to make decisions that will alter your future," he said.
The five tales he ultimately plotted are that the youngster would grow up to be a strident evangelical minister, a moneygrubbing investment banker, a soldier, a mom-and-pop store owner and someone who is homeless and gay.
Musically, Anderson opted to go back to the future by using hardware that appeared on the 1972 disc.
"I wanted to keep the same sonic values," he explained. "I think that's important. I wanted to work with the same classic instruments of rock music - to reuse the Hammond organ and Leslie speaker cabinets, the Marshall speaker cabinets, the Gibson Les Paul guitar and the Fender jazz bass. Along with, of course, the instruments I play - the flute and the little parlor guitar and a few other odd bits and pieces here and there."
For the past decade-and-a-half, Anderson has toured the world annually. However, most of the road trips have been billed under his name, not that of Jethro Tull. He reasoned that the Tull name signals to the public that the program will consist of the band's most familiar tunes, among them "Aqualung," Locomotive Breath," "Bouree" and "Living In the Past." These shows, he suggested, are likely to attract unruly, alcohol-fueled "fans" who can ruin a show for artist and audience alike.
On the other hand, he continued, people who come to Ian Anderson concerts are more "respectful" and allow him to stretch beyond the "greatest hits" mentality.
Not that the Tull brand has been buried for good.
"I'm pretty sure," he admitted, "it will come up sometime in the next years, if not months."
Caesars Atlantic City, Boardwalk at Arkansas Avenue, 9 p.m. Saturday, $80-$120, 800-736-1420, ticketmaster.com.
Contact Chuck Darrow at 215-313-3134 or firstname.lastname@example.org. Follow him on Twitter @chuckdarrow and read his blog philly.com/casinotes.