Lady Gaga has joined Apple Music! Mother Monster took to her Twitter account on Tuesday to announce that she is a part of the new streaming music service and congratulate Tim Cook and Jimmy Iovine on the positive first reactions to the project. "So happy for Tim, Jimmy and everyone at Apple Music and Beats1," she tweeted. "I'm excited to be a part of it." Apple Music is a new music streaming service unveiled by Jimmy Iovine at the WWDC event in San Francisco on Monday. The new app combines a mus