Two and a half years ago, the legendary European music festival Primavera Sound — which is based in Barcelona and has maintained a sister festival in Porto for years — announced its intention to launch an annual event in Los Angeles. Since then, a global pandemic has prevented even the flagship Primavera from taking place. But the organizers are back today with news of the debut Primavera Sound LA, set for Sept. 16-18 at LA State Historical Park.