Earlier this year, DJ Mustard — he’s been just Mustard for years, but most of us still call him DJ Mustard — produced Kendrick Lamar’s convulsive Drake diss “Not Like Us.” Mustard has tons of hits to his name, but this was his first time producing one that reached #1. On Wednesday night, Mustard took part in Kendrick Lamar’s euphoric Pop Out show, bringing out a parade of West Coast stars and then joining Kendrick for the triumphant finale. That night, Travis Scott was otherwise occupied. But now, Mustard and Scott have a new song together.