Following the success of his major label debut, good kid, m.A.A.d. city, in 2012, the rapper Kendrick Lamar's long-awaited follow-up, To Pimp a Butterfly (TDE/Aftermath/Interscope), is about carrying the weight of that clarity: What happens when you speak out, spiritually and politically, and people actually start to listen? And what of the world you left behind?