Dancing, singing and brandishing sticks, in helmets and brightly coloured overalls, they form a spectacle greater than the sum of its parts. But this is not another defiant show from miners in South Africa's troubled platinum belt. It is a dress rehearsal.

Sitting in the stalls of Pretoria's State Theatre are Lucas Ledwaba and Leon Sadiki, co-authors of a book about the darkest day in the country's post-apartheid history: the police massacre of 34 striking workers at Marikana in 2012. Before their eyes it is being adapted into a most unexpected and provocative work of art: Marikana: the Musical.

Ledwaba, a journalist, and Sadiki, a photographer, were reporting on the strike at the Lonmin platinum mine in Marikana two years ago when they witnessed the carnage. "Although there was a lot of tension, no one imagined we'd be talking about 34 killed in 20 minutes," said Ledwaba, 39. "We saw people die. Even today it has left a lasting impression on our lives."

They co-wrote a book, We Are Going to Kill Each Other Today, and approached the State Theatre with the idea of turning it into a musical.

Ledwaba said: "It was only after writing the book I realised the story has to be told in another medium. It has to reach as many people as possible. If we keep quiet and don't want to speak about it and dramatise it, we are doing a disservice to our country and the people who were killed. People need to know what happened. In apartheid we had protest theatre. There were books and films, but theatre had the most impact. It's interactive and personal and you can't take it back. It has a way of conveying emotion more than any other medium."

With a cast of more than 20 actors and five musicians, Marikana: the Musical premiered at the National Arts Festival in Grahamstown recently and opens at the State Theatre in October. Its director, Aubrey Sekhabi, hopes it will also be performed in Marikana itself.

Sekhabi was at the Edinburgh festival when he heard about the shootings. "I switched on the TV and it was playing over and over again. I sat there and said: 'What! What!' It should be a big wake-up call for us. Maybe we are too laid back, too compliant. We need to survive this.'"

Sekhabi and composer Mpho Matome faced a challenge to capture the right tone, and some critics in Grahamstown suggested they had failed to escape the "celebratory" essence of musicals. But the British show Billy Elliot, set in a northern mining town against the background of the 1984-85 miners' strike, is a reminder of what the form can achieve.

"It's a South African musical," Sekhabi said. "We sing to mourn, to heal, to rejoice. Our pain, our miseries, we sing. When the miners were out there on the koppie [small hill] in Marikana, they were telling their frustrations through song. The whole event is very emotional. You can get to those emotions right away with music, instead of building slowly through drama. It's so big and it has so much soul."

In one scene, drawn directly from the book, a father in a village asks to be allowed to weep for his late son, despite local attitudes that men should not cry in public.

Sekhabi, 45, said it was not his desire to attack the police, government or mining companies over that day, which is the subject of a long-running judicial commission of inquiry. "The book tells it as it is. It doesn't try to take sides. We should heal and you can't push Marikana aside. We have to deal with it as a nation. If we're able to forgive the Nats [National party] for Sharpeville and Soweto, we should forgive each other for this terrible thing. So we learn from it and don't repeat the mistakes."

The sentiment was echoed by the actor and singer Aubrey Poo, who plays the police commander Nyoka, inspired by a real-life counterpart but not intended to be the villain of the piece. Taking a break from rehearsal, police baton in hand, the 34-year-old said: "It doesn't point to anybody, but it brings to the fore the pain the tragic event cost. Otherwise it would be propaganda. It speaks to hearts and minds."

Poo starred as Nelson Mandela in the opera Mandela Trilogy. "The beautiful thing about musical theatre, and why The Lion King would run longer than a straight play, is because music is more immediately accessible and reaches people who wouldn't otherwise go to the theatre," he said.

"In musicals, that's when you sing: it's when normal dialogue would fail you. The emotions of this story allow us to sing."