From The Verge:
The Tweet the Beat feature started appearing on the weekend, and it automatically displays a fullscreen pop-up ad for mobile Spotify users with pre-populated text and a button to tweet Rihanna with a thanks for her “Bitch Better Have My Money” single. Spotify is also displaying the same pop-up on desktop clients, encouraging users to fire off tweets. The pop-ups appear randomly when searching for or playing music. While Spotify’s free service includes ad-supported streaming, its premium subscription ditches ads altogether for a $9.99 monthly fee. Spotify premium users will also receive Tweet the Beat ads.
A Spotify spokesperson confirmed the new feature to The Verge, noting that it started rolling out on Saturday with just Rihanna involved so far. “What you’re seeing is a new feature called Tweet the Beat which lets listeners express love and appreciation towards the artists they follow or listen to often, and has been designed as a great way for fans to get closer to their favourite artists.”