Which pioneering machine learning feature did Spotify introduce in 2015 that revolutionized music marketing and discovery?

The music industry has been transformed by advanced machine learning algorithms that power streaming platforms. These AI systems do much more than simply recommend songs - they're reshaping how artists reach audiences, how marketing campaigns are targeted, and how music is discovered. Test your knowledge of how machine learning is changing the business of music consumption and marketing.

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Discover Weekly, which uses collaborative filtering and natural language processing to create personalized playlists
Sound ID, which analyzes audio frequencies to match listeners with songs sharing similar acoustic patterns
Genre Predictor, which automatically categorizes new releases based on machine analysis of musical elements
Viral Vector, which uses social network data to predict which songs will achieve mainstream success