The story of Motown has proved dependably compelling through the decades — a rags-to-riches tale regularly revisited in documentaries, books, even a Broadway musical.

Through it all, one important voice was rarely heard: that of Barney Ales, the Detroit-born sales chief and Berry Gordy confidante who helped propel Motown’s music onto the mainstream airwaves and record shelves.

Ales’ memories from behind the scenes are now the heart of “Motown: The Sound of Young America,” a visually rich, 400-page volume set to hit stores on Tuesday, several months after its U.K. release.