Those who were around in the 1980s might remember and appreciate The Specials AKA:

http://fixyt.com/watch?v=AgcTvoWjZJU

For those who weren't: this song protesting Mandela's incarceration got widespread airplay around the world. I'm not sure I can recall a similar case of popular music taking on a case of protesting for the freedom of a single individual, and suspect it played a large part in waking consciousness to the inequity of Apartheid and much of the pressure which was brought to bear in the late 1980s against South Africa.