This is a book about a hip-hop producer who changed the path of popular music. The career of James Dewitt Yancey was short, lasting around a dozen years-from his first release in 1993 on a small record label in his home- town of Detroit until his death in Los Angeles in 2006 at the age of thirty- two from a rare blood disease. In that time, no record he produced rose higher than #27 on the Billboard Hot 100 chart. That fact is remarkable because Yancey-first known as Jay Dee and then as J Dilla-collaborated with some of the most popular artists of his time, like A Tribe Called Quest, Busta Rhymes, the Roots, D'Angelo, Common, and Erykah Badu, and influenced the music of superstars like Michael and Janet Jackson. What's more, J Dilla continues to inspire and provoke new artists who rose to fame after he died, from the rap icon Kendrick Lamar to the jazz pianist Robert Glasper to dozens of pop acts. When you ask J Dilla's more successful hip-hop contemporaries like Dr. Dre and Pharrell to name peers they admire, Dilla is always near or at the top of their lists. Despite his short life span and low profile, J Dilla was, and remains, the producer's producer, the inspiration for inspirers, or, as the Roots' drummer Ahmir "Questlove" Thompson says, "the mu- sician's musician's musician."