Imagine an utterly unremarkable upright piano, hazelnut brown, standing on the pavement in front of a museum, a theatre, a prison or a school. Would you stop, or would you glance at it momentarily and walk on by?

Then imagine that on this piano one of the most resonant songs of the 20th century was composed and that it stands at the scene of a shocking act of violence.

Welcome to the Imagine piano tour, the brainchild of singer-songwriter George Michael and his partner Kenny Goss, who runs a Dallas art gallery, and featuring the piano bought in 1970 by John Lennon and put in his studio in Tittenhurst Park, Berkshire.

It was on this nondescript-looking instrument a year later that he wrote the song that would become the anthem of peaceniks everywhere, Imagine. Now it is being carted across the US - carefully, by specialist removal people - in a symbolic road trip for peace.

On Saturday it was placed outside the Ford's Theatre in Washington where 142 years earlier Abraham Lincoln was shot as he watched a performance of Our American Cousin. Last week it was outside the Texas State Penitentiary at Huntsville during the execution of a death row prisoner, and before that it was in Dealey Plaza in Dallas, Texas, and at the Lorraine motel in Memphis, Tennessee, on the anniversaries of the assassinations of John F Kennedy and Martin Luther King respectively.

Michael bought the piano six years ago for £1.5m - a record price at the time for pop memorabilia. Having bought in, as it were, to the history of the song, the couple felt it would be wrong to leave the piano languishing in their front room and the idea of taking it to places where extreme acts of violence had taken place or were taking place was born. "By taking the piano to all these sites, we are reminded that violence has long been a part of our history," Michael said.

Caroline True, who is organising the tour, said the experience had been humbling. People had travelled many miles to see the piano and the reaction had been universally positive. Outside Ford's Theatre, actors and crew gathered round the instrument to perform Imagine. "The idea is so simple and so effective in getting through to people. We are not being political or opinionated, we are just spreading the image of peace," Ms True said.

Next week the piano will be exceptionally busy. On Thursday it will take part in the service commemorating the Oklahoma bombing in which 168 people died 12 years ago, travelling the same day to Waco, Texas, for the 14th anniversary of the deaths of nearly 80 people in the police siege of a religious sect. On Friday it is likely to be standing in front of Columbine High School where eight years ago 12 students and a teacher were killed in a shooting spree.

A video of the piano's escapades will be made into an installation artwork and a book of photographs is planned. Then a trip is envisaged to Auschwitz and then the Tower of London and the locations of the 2005 London bombings.