Music is increasingly an ecosystem of cults and tribes and microscenes. Some of them grow big enough to be mistaken for the big boxes of old. But for the most part, category-killing artists—true, undeniable superstars—have become a thing of the past.

Pitchfork has been a key engine for identifying and nurturing any number of baby movements. It feeds them until they can stand up on their own, in the hope of producing a few acts that can perform here. The festival has something of a symbiotic relationship with the Web site, each validating the other’s existence.