The Impressions -- Curtis Mayfield, Sam Gooden, and Fred Cash -- sang People Get Ready in 1965, a year after the Civil Rights Act. It was a gospel song about a train to freedom. It was a pop hit. It was both. That was the genius. The Impressions didn't just sing about the movement. They were the movement.

Curtis Mayfield was the voice and the songwriter -- a gentle falsetto and a pen that wrote Keep On Pushing, We're a Winner, and People Get Ready. Before Superfly, before Move On Up, before Curtis became the conscience of a generation, the Impressions were laying the foundation. Three-part harmony that sounded like church, songs that sounded like the future.

When Curtis left for a solo career, the group kept going. When the hits stopped, the songs kept going. People Get Ready has been covered by Bob Marley, Rod Stewart, and dozens of others. The train is still boarding.

The Impressions -- Curtis Mayfield's first group. People Get Ready. We're a Winner. The civil rights movement's soundtrack set to three-part harmony.