* Music-centric social services account for 70 pct of revenue (Recasts and writes through with earnings figures): HONG KONG (Reuters) - Tencent Music Entertainment, which owns China’s most popular music apps, has filed for a U.S. IPO seeking funds to develop content and new services, in what is expected to be one of the biggest U.S. listings by a Chinese company this year. The music arm of tech giant Tencent Holdings (0700.HK), which plans a Nasdaq listing, set a placeholder amount of $1 billion for registration purposes. Sources said last month it was hoping to raise $2 billion.