Drake left so few of his doleful folk songs that this collection of rarities is a genuine treasure chest. “Rider On the Wheel” and “Tow the Line” reiterate the orchestral sense of tension he could create with a single acoustic guitar, and amid the alternate takes are “Thoughts of Mary Jane,” featuring Richard Thompson’s guitar curlicues, and an early, unadorned “River Man” from 1968. But the record’s true dark heart is “Black Eyed Dog,” a skeletal wail of fear set to a scratchy, jittery drone.