Youssou N'Dour's Protest Song

Dominic Nahr / Magnum for TIME

Crowd puller N'Dour is surrounded by supporters at a demonstration in Independence Square, Dakar. Police used tear gas on protesters

There's a tang of tear gas in the air as Youssou N'Dour pops up through the sunroof of his car.

Africa's most famous living musician is on the edge of Independence Square in downtown Dakar, Senegal, surrounded by 50 journalists and 100 supporters and, beyond them, a line of 100 riot police fingering plastic bullets and a water cannon mounted on an armored truck.

Behind N'Dour the police truck is...