On Friday night, música mexicana band Grupo Firme surprised the crowd at their show in Austin with an unexpected special guest: Demi Lovato. Yes, you read that right. Lovato hit the stage with frontman Eduin Caz to duet their upcoming single, “Chula.” Mid-set, Lovato, who is on the heels of back-to-back rock projects, joined the “Ya Supérame” group for ...