John Lennon once called it “’Working Class Hero’ for conservatives,” and indeed, it challenges the status quo at its most fundamental.

So said John Lennon about “Imagine,” the most successful single of his solo career. The song has been covered by artists in every genre, from Liza Minnelli to Stevie Wonder to Neil Young to Lady Gaga, and performed at some of the biggest events across the globe. The Olympics. New Year’s Eve. Concerts for Peace. Concerts for Hunger. This year, at the tribute concert in honor of what would have been Lennon’s 75th birthday, Willie Nelson performed it to an audience of fans and fellow superstars.

The impact of the song is unquestionable, most recently finding new poignancy when pianist Davide Martello drove 400 miles from Germany to Paris so he could play it outside the Bataclan theatre, where 89 people were killed by terrorists last month. But disguised within its message of peace and love and its flowing piano melody is a collection of edgy, “dangerous” ideas that challenge society as we know it. The sweet, sweet song that has become an anthem all over the world is actually full of controversial lyrics and radical ideas. John Lennon once called it “’Working Class Hero’ for conservatives,” and indeed, it challenges the status quo at its most fundamental.

John Lennon composed the song in one session, sitting at his white grand piano in Tittenhurst Park estate in England. Yoko Ono watched him as he played the melody and wrote most of the lyrics. He recorded it in his home studio with help from musicians Alan White, longtime Beatle friend (and artist behind the cover of the Revolver album) Klaus Voorman, Nicky Hopkins, and producer Phil Spector, who uncharacteristically kept the track fairly simple. They experimented, at one point having Hopkins play on the same piano as Lennon, but on a higher octave. The more they added, the more they ended up stripping away. You can watch them recording it in this excerpt from the documentary Gimme Some Truth: The Making of John Lennon’s Imagine Album.