Music social networks play a role in the diffusion of music. There are different ways a piece of music reaches people in a network: through the influence of social connections or via the discovery of external information, such as mass media, newspapers, etc. This empirical study uses over 10 months of user listening data from a music social network to examine the effects of external information on streaming music diffusion at the macro- and micro-levels. The data include weekly listening records for 557,554 users. Our results suggest that external information is a significant driver of increased streaming music diffusion, in comparison to in- network influences. We also found evidence of variation in the different influences, such as for a scale effect, the validity and type of information shared, and the impact of geolocation. These insights can be used to promote music and design personalized music recommendations.