When people move, it’s not just people, and a suitcase full of clothes, and a few pictures. Their culture comes with them, including their music. Chicago Blues — electrified and raw — didn’t come from thin air. It came from musicians who were part of the Great Migration. A new work by NPR’s Cheryl Corley and musician Lucy Smith chronicles the history and showcases the sounds of the players who made their way north, laying the foundation for the music that still lives today.