Miley Cyrus and her model "friend" Justin Gaston are now making music together! "I'll tell you what -- they are great friends, and they make a good team," Miley's dad Billy Ray tells US Weekly at Monday's premiere of Bolt, which includes voice-work by Miley. "They write a lot of songs together, and they sing -- it's incredible." What advice does Billy Ray have for Miley these days? "Make good choices. Do the best you can do -- mostly have fun. I always tell her that as long as she's having fun, then it's working. When it starts being work, then it ain't working," he says. "She loves what she's doing. She has a real passion for making music as an artist. She loves being an actress, and we all feel very fortunate being in the Disney family and getting to do both of our loves."