Sly Stone was a musical alchemist, combining soul, funk, and psychedelic rock with elements of gospel, jazz, and Latin music to create the new sound of the 1960s. With his prodigious Afro and platform boots—a look that one critic described as “the wildest pimp on the block”—he was an onstage dynamo as leader of the multiracial, mixed-gender band Sly and the Family Stone. From 1968 to 1971, the group scored hits with buoyant songs such as “Dance to the Music,” “Everyday People,” “Hot Fun in the Summertime,” and “I Want to Take You Higher,” and influenced artists such as Prince, Stevie Wonder, and Miles Davis. But Stone, an eccentric whose songs of uplift were tempered by darker themes of struggle and disillusionment, had a fall as steep as his…