NEW YORK — The manuscript for one of the most popular sing-along tunes at bars, “American Pie,” will go on auction this month. The asking price: at least $1 million.

Christie’s in New York will sell 16 pages of Don McLean’s handwritten lyrics and typed drafts for his enigmatic 1971 hit about the American zeitgeist in the latter part of the 20th century. The high estimate for the April 7 auction is $1.5 million.

“‘American Pie’ has lasted 45 years now,” McLean, 69, who lives in Camden, said in an interview. “Relevance is a hard thing to predict.”

Rock memorabilia collecting is popular among wealthy baby boomers who are looking for alternative ways to invest. The most sought-after manuscripts are from the Beatles and Bob Dylan, said Leila Dunbar, a former Sotheby’s executive who is a memorabilia appraiser and consultant in New York.

Dylan’s “Like a Rolling Stone” sold for more than $2 million in 2012, and the Beatles’ “A Day in the Life” sold for $1.2 million in 2010. Both were sold at Sotheby’s.

The “American Pie” manuscript is a “wild card” because those other artists had more hits than McLean, Dunbar said. Still, “these are lyrics that have touched a lot of people and have mystery to them.”

The symbolism of “American Pie” has long eluded listeners who try to decipher the complicated lyrics of the 8-minute, 36- second song that opens with “a long long time ago,” and goes on about “a generation lost in space” and “the day the music died.”

McLean said he rarely comments on the song’s meaning because he wants people to interpret the lyrics themselves. He said he tried to simulate the feeling of a dream and “capture something that you cannot express.”

The manuscript doesn’t outline his intent, either, but “when you read it, you realize it’s just me going in a lot of different directions,” he said. “I try to have a bunch of different points of view about it.”

McLean said he’s selling the manuscript because “my wife and children don’t seem to have the knack for making money, and I seem to have that.” He said he plans to hold a larger sale in about two years that includes a wider array of his memorabilia and other items he’s collected in the past decades.

The manuscript, which he wrote partially on legal paper he found in a Manhattan trash can, was stored in “a banker’s box in my library on the third floor of my house where I would toss work products from songs for albums through the years,” he said.

The buyer will probably be a private collector because museums usually can’t afford memorabilia with such a hefty price tag, and items in the Rock and Roll Hall of Fame are almost all donated, said Warwick Stone, a curator for the Hard Rock Hotel Las Vegas’s memorabilia collection.

Chinese buyers have shown an interest in American pop culture memorabilia, particularly items from Michael Jackson and Marilyn Monroe, he said.

“They’re driving the price up like crazy,” Stone said. Christie’s held an exhibit in Tokyo of the manuscript on March 25 and 26. The documents will be on view at Christie’s in New York April 2 to April 6.

McLean, who lives in Camden, Maine, and starts a tour of Britain, Ireland, and the U.S. in May, said he “couldn’t care less” who buys the lyrics. “They’re not mine anymore,” he said. He said he won’t attend the auction.

He said if he could own another musician’s manuscript, it would be one by George Gershwin or Irving Berlin. His own music resonates with listeners of any age, he said.

“It’s a family song,” he said. “It gets passed down from generation to generation.”