Dhaka, Dec. 30 -- "They hear it come out, but they don't know how it got there," she says as she readies herself to record in a Chicago studio in 1927. "They don't understand that that's life's way of talking. You don't sing to feel better, you sing because that's your way of understanding life."

Time seems to roll to a stop as Rainey speaks. The divide between her words and what white society is ready to hear lays itself out wide before us. That, you realise, is the fertile space where her music exists - an ungoverned territory, too filled with spirit, expression and abstention for politics and law to interfere.

But maybe this scene is only so startling because of how rare its kind has been throughout film history. The movies have hard...