If Danny Brown’s charms have ever reduced you to debilitating giddiness, don’t watch until the end of his Jimmy Kimmel Live! performance from last night. That’s when the endlessly nimble Detroit MC hugged guest vocalist Megan James, from ghostly electronic-pop duo Purity Ring, and grinningly assured her, “Baby, you did great, baby!” — then turned back to the crowd, tongue wagging and index finger in the air. Both artists were making their TV debut, and the triumphant conclusion was well deserved: The duo’s take on their powerfully emotional Old trap-dirge drama was sharp and compelling, James’ stately incantantions weirdly complementing Brown’s rapidfire, detail-rich storytelling. It’s the latest chapter in an improbable collaboration that began with Purity Ring’s 2012 “Belispeak II.” These days Brown is just as likely to be seen collaborating with Vampire Weekend or (really) Bob Dylan, while Purity Ring have been working with Lady Gaga and techno producer Jon Hopkins.