On Age of the Ram, the country singer completes his “Sagebrush Trilogy” by cementing his relationship with producer Shooter Jennings and finding himself in the story of a rodeo cowboy

In 1963, Marty Robbins released a rodeo tune called “Old Red.” The title is the name of an ornery bull that had “never been rode” until he drew Billy McLane, a brash young cowboy who had “never been …