NEW YORK - DECEMBER 11: (ITALY OUT, NY DAILY NEWS OUT, NY NEWSDAY OUT)  Flowers and a photo of musician, John Lennon, lie at
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The day after terrorist gunmen took the lives of over 80 music fans at an Eagles of Death Metal concert at Paris’ Le Bataclan, a bicyclist towing a piano pulled up in front of the theater, jumped behind the keyboard, and played John Lennon’s iconic 1971 ballad, “Imagine.”

The song is so immediately familiar to young and old that the pianist, 34-year-old German resident Davide Martello, didn’t even need to sing the words to share his message. As he played the melody, Lennon’s words likely sprang into the minds of the gathering crowd,  “Imagine there’s no countries / it isn’t hard to do / nothing to kill or die for … Imagine all the people, living life in peace.”

Hours earlier, in the immediate wake of Friday’s attacks, British band Coldplay was in Los Angeles performing the same song, with Chris Martin singing those famous words.

Time and time again, the world has turned to this deceptively simple song when terror, war, deprivation and violence has erupted. BMI named “Imagine” one of the most performed songs of the 20th century. Patti LaBelle played it at the massive African hunger benefit Live-Aid in 1985. Stevie Wonder played it at Atlanta’s 1996 Summer Olympics in tribute to the victims of the bombing at Centennial Olympic Park. Neil Young covered it during the televised September 11 benefit just days after the 2001 attacks. Elton JohnQueen, and scores of grieving New York fans reacted to the 1980 murder of John Lennon himself by spontaneously turning to “Imagine.”

But why this song, of all the millions of anthems in the universe? And how does a 44-year-old piano ballad endure like this across continents and generations? The answer is one word: hope.

“Imagine” is not a mindless plea for peace, a dour elegy for victims, or simply a song against the Vietnam war. It’s a thoughtful, straight-forward message of belief that things can be better if we all believe it’s possible, and that we all have the power to believe it’s possible. “If you can imagine a world at peace,” Lennon told journalist David Sheff in one of his last interviews, “then it can be true.”

But it wouldn’t have been nearly as powerful — or iconic at all — coming from anyone but Lennon, because his voice and experience resounded as real. Lennon, born working-class literally during an air raid attack on England during World War II, was also an immigrant who fought for years to become an American. When Neil Young invoked the song after 9/11, the memory that Lennon had been a New Yorker slain by violence in addition to an outspoken peace activist echoed throughout the performance.

Lennon, the formidable songwriter and Beatles rhythm guitarist, knew the might of an easy melody paired with a smart message in plain language. Sure, 1969’s “Give Peace A Chance,” 1971’s “Power To The People” and “Happy Xmas (War Is Over)” stand as proof of this idea, but “Imagine” was his masterpiece of this form. Pop, rock, R&B and classical musicians—from beginners to experts—can manage the chords to “Imagine.” Anyone can sing it, too.

Hope. Dig into why “Imagine” is the song the world turns to in times of trouble, and you’ll also see it’s now the song the world turns to in times of peace, positivity and progress, especially for younger music artists and fans in the 21st century. It’s been part of the festivities in Times Square as New York rings in New Year’s since 2005. India.Arie performed it at the 2010 Nobel Peace Prize concert with Herbie Hancock. It’s also been performed at the 2012 Olympics (by the Liverpool youth choirs) and the 2015 European Games (by Lady Gaga), underscoring those events’ missions of international understanding.

“You may say I’m a dreamer, but I’m not the only one,” 30-year-old Lennon wrote at that piano back in the day. “I hope someday you’ll join us and the world will live as one.”

Fast-forward to November 13 and 14, 2015, as both a British band and German pianist again reminded us to look toward the light with Lennon’s words.

“I can’t bring people back but I can inspire them with music and when people are inspired they can do anything,” pianist Martello told The Guardian. “That’s why I played ‘Imagine.’”