Which music retail innovation was the first to use a 'recommendation engine' that suggested products based on previous purchases, revolutionizing music discovery in the early 2000s?

The music retail landscape has transformed dramatically in recent decades. From vinyl shops to digital streaming, the industry has seen revolutionary changes in how music products are sold, marketed, and consumed. This poll tests your knowledge about a significant retail innovation that changed how consumers discover and purchase music, creating an entirely new business model in the process.

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iTunes' Genius feature
Amazon's collaborative filtering system
Spotify's Discover Weekly
Pandora's Music Genome Project