Bruce Hornsby, legendary pianist, singer, and songwriter, discusses his humble beginnings in a Grateful Dead cover band and his graduation to a Doobie Brothers acolyte to his mega breakthrough with “The Way It Is” to his time as an actual member of the Grateful Dead and his resurgence, resonating first with hip-hop artists like 2Pac, and more recently with younger indie rock artists like Bon Iver and Vampire Weekend. His latest album is “Flicted.”