Beats Music streaming music service arrives on the 21st

Jimmy Iovine, whose career as a recording engineer, producer and music executive stretches from John Lennon to Lady Gaga, was proudly showing off some of his hits one afternoon last month at a boutique recording studio here. He passed through rooms where Eminem and Gwen Stefani made records and pointed to the console on which Dr. Dre recorded his landmark 1992 album, “The Chronic.” The studio walls were crammed with pictures of Steve Jobs, Bono and other celebrities sampling the bass-heavy Beats by Dr. Dre headphones, which — at up to $450 apiece — have become a billion-dollar success story.