Think you know all about hip-hop? Think again. Different styles have evolved since hip-hop’s ’70s origins in the African American neighborhoods of the Bronx and later the Latino enclaves of Queens, and they get lumped together, says Rennie Harris. What makes the Illadelph festival unique is that many of his 15 teaching colleagues are originators of the form; these “Legends” provide the specifics of hip-hop history, theory and technique. “That’s why we stay on the foundation,” Harris says, so students can “take it, build on that, and do their thing.”