“The smooth criminal on beat breaks / Never put me in your box if your shit eats tapes,” rapped Nas on his 1994 classic “N.Y. State of Mind.” Like other underground genres that hit their stride in the previous decade, hip hop relied on low budget cassette tapes to spread its message, infecting young listeners like a virus. Evolving from amateur live recordings to professionally-produced CD compilations, the “mixtape” soon became a pillar of hip hop culture, showcasing both emerging and established artists. Predictably, when the music industry finally caught up with what was happening out on the streets, it quickly ruined everything.