Basically, the streaming service will allow companies to control the messages "end-to-end," which was possible before in editorial playlists like Rap Caviar, but not for Discover Weekly. Given the popularity of the personalized playlist that helps you find new music each Monday, brands were surely champing at the bit to fully customize every aspect of the messages Spotify users will see and hear there like they could elsewhere on the streaming service.

"Personalization has quickly gone from a nice-to-have to an expected consumer experience that delights audiences and marketers are craving opportunities to be part of it," Spotify's global head of partner solutions Danielle Lee explained. "Our new Discover Weekly ad experience positions advertisers for success and ensures that our fans are hearing messages that embody the ethos of discovery."

Since machine learning is a key part of Discover Weekly's curation, it makes sense that Spotify would want the first company who took a crack at these new personalized messages to share an affinity for that technology. Enter Microsoft. During the beta phase of this Discover Weekly ad expansion, Microsoft's "Empowering Us All" campaign will broadcast messages about how AI can impact all aspects of life -- including education, healthcare and philanthropy.

"When people think of Spotify, they think about music -- all of the world's songs, albums and their favorite playlists right at their fingertips. At the same time, Spotify is a technology company," said Casey Weinreich, Spotify's head of industry, tech. "The magic with this partnership is we were able to identify a tech partner with a shared ambition to utilize technology, in this case machine learning, to enrich our user experience."

Soon Spotify will open up this option to other companies, so you can expect to hear more detailed and custom-tailored messages in Discover Weekly. That is, if you're a free user.