 But the researchers theorize that genres like stadium rock, disco, and hip-hop have become more complex in other ways. So it's possible the melodies have become simpler to compensate for that. For NPR News, I'm Vicki Barker in London. The Dalai Lama turns 89 today. The Tibetan spiritual leader and Nobel laureate underwent knee surgery in New York last month and is currently recovering in the U.S.,