What makes a viral song? Unraveling music virality factors

The viral phenomenon is present in several contexts, combining the advantages of streaming platforms and other social networks. Music is no exception. Viral songs are widely shared in a short amount of time, and they may become successful by reaching the top of the charts with millions of streams and digital sales. However, not all songs that go viral become hits, as the sharing process is not enough to be converted into streams. In this work, we analyze viral and hit songs as two different yet interconnected aspects of music popularity. Specifically, we aim to uncover factors that are relevant to distinguishing viral from hit songs. We evaluate three research hypotheses related to musical features, and the results reveal that considering only acoustic and other intrinsic features is not enough; and extrinsic features (e.g., artists' genre and the time from the release to the first chart entry) are essential in achieving such a goal. Moreover, artist-related and temporal features are among the most relevant indicators to differentiate hit and viral songs. Overall, our findings offer relevant insights for understanding the dynamics of music consumption and its sharing on online platforms, as we reveal important factors that describe what makes a viral song and what differentiates it from a hit.