'wearing calipers, so as to avoid both conscription and facing the indignities suffered by more genuine COs'#

Except of course he didn't avoid conscription.

'the South African struggle was well accounted for in the revolutionary music of radical exiles such as Dudu Pukwana, Chris MacGregor, Johnny Mbizo Dyani, Shimmy Radise, Abdullah Ibrahim etc'
What anti-apartheid message was being put across in the jazz played by those mentioned above?