When Lapiro de Mbanga wrote his most famous song it was in despair at the way he saw his country being ruined by a president making constitutional changes to stay in power indefinitely.
When his fellow Cameroonians took to the streets of the major cities for four days of violent unrest in 2008, it was De Mbanga's song they adopted as their unofficial anthem.
The lyrics of Constitution Constipée, criticising President Paul Biya as "caught in the trap of networks that oblige him to stay in power even though he is tired", earned its songwriter a prison sentence. De Mbanga was charged with inciting youth unrest and is still in prison in Cameroon. He was also ordered to pay a fine of $640,000 (£400,000) as compensation for damage caused during the protests.
Music has always been the stuff of rebellion, but under some of the world's harshest regimes singers are increasingly becoming the victims of censorship and threat as much as opposition politicians, journalists and writers. But their plight is often far less acknowledged.
Now a project to recognise the contribution of some of the world's most important protest singers has been pulled together by a woman who was forced to give up performing on stage because of threats made on her life. Listen To The Banned is an album including the work of 14 international artists, all of whom have experienced imprisonment, censorship, harassment or violence because of their music.
Deeyah, a classically trained singer born in Norway, of Pakistani and Afghan parents, had a burgeoning career in pop music when she had to leave Norway because of harassment and disapproval from hardline Islamic groups. She moved to the US and then the UK, but gave up the limelight when the threats and antagonism proved just as strong wherever she went.
"In the end I decided the threats were not fair on my family. But during the troubles I went through I came across the Freemuse group, which works for censored artists and I got really interested in what they were doing and the astonishing back stories to some of this tremendous music that was being made. I came up with the idea of putting some of the best music together with them," she said.
A two-year project culminated in the album, which is available fromFreemuse.org. Giving De Mbanga an award last year, the renowned Israeli conductor Daniel Barenboim argued that music such as his "constitutes a cultural megaphone by which the disenfranchised and politically endangered can vicariously exercise free speech".
Deeyah said: "Censorship of music seems to be forgotten. I don't know if it is because people think of music as entertainment, so it is valued less that journalism or politicians or writers.
"I don't know why imprisoning a filmmaker is seen as any worse than imprisoning a songwriter, but it does seem to be the case. But music is such a part of our culture, our heritage, our traditions, of who we are. Which is why so many regimes find it so threatening."
Tiken Jah Fakoly, a singer from Ivory Coast who has been forced into exile, said: "Normally people get trophies for selling most records, but this CD highlights artists who fight for justice."
Abazar Hamid, a Sudanese songwriter now living in exile in Egypt, said: "Listen To The Banned has empowered me to face censorship and let me trust on my music and feel I am not alone."
Mahsa Vahdat of Iran said that she was encouraged by being part of the project. "I am honoured to be part of this, we are invisible and hidden voices that can impress the world and can elevate the feeling of life," she said.