Pandora is best known for the Music Genome Project, the most unique and richly labelled 1.5 million+ song data. Naturally a content based approach to music recommendation is used as the foundation to our online radio service. Over the years we have improved and transformed the recommendation platform to incorporate multi-facted data and models on this foundation. Combined with a dynamic ensemble system, this platform now powers the most popular streaming music service in the U.S., with 77 million+ monthly active users. In this talk I will discuss the music recommendation topics we work on at Pandora such as our ever evolving machine learning tasks, give examples on user modeling tasks, and share challenges we still face.