Blues … Black … Darker than grey/ Creation sounds Gold Reef Mine rockfall crush-sounds/ Guitar-string gun-spit tear flesh/ Black sonic science/ Darkest Acoustics … (from Where Are The Keys? on Group Theory: Black Music) SOUTH African poet Lesego Rampolokeng often writes about Black music in his poems. His collaborations with musicians on record are rarer but always remarkable. There was the cassette-only 1994 African Axemen collaboration with Zimbabwean Louis Mhlanga and a stellar crew of other pan-African guitarists. And his Tears for Marikana on Salim Washington’s album, Sankofa. And now the track Where Are the Keys? on South African drummer…