Grammy-winning mix engineer and alumnus Miles Walker opened his Atlanta studio to a group of students visiting the music hub while on spring break last week. In addition to arranging tours of other area studios, he let them observe a recording session at his own Parhelion Recording Studios. Walker, who earned Grammys for his mixing on Rihanna and Beyoncé records, took time out to talk about his Berklee experience and the Atlanta market, as well as offer some sage advice to today’s students.