Which innovative marketing strategy was most instrumental to Spotify's early global growth and brand recognition?

Spotify revolutionized the music streaming industry with innovative marketing approaches. In its early growth phase, the company employed a particularly clever strategy that helped it rapidly expand its user base and stand out from competitors like Pandora and Apple Music. This strategy has since been studied in marketing courses worldwide as an example of effective digital-age brand building in the music industry. Can you identify which marketing approach was most crucial to Spotify's initial global success?

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The freemium model with ad-supported tier that allowed users to experience the full platform before committing to a paid subscription
Their exclusive podcast deals with major celebrities like Joe Rogan and the Obamas
The annual 'Wrapped' personalized user listening data campaign that began in 2015
Their heavy investment in television advertising campaigns featuring popular artists