Pandora’s competitor, Spotify, has been in this space since May 2015, allowing advertisers to buy based on the emotions and hypothesized activity its listeners are feeling and performing. A Spotify spokesperson did not immediately return a request for comment.

What sets Pandora apart from the competition, its execs say, is that the service has been tagging each song based around potential emotions since the service’s beginning. For over two decades, real humans have been cataloguing the songs with keywords, said Lizzie Widhelm, svp of ad innovation at Pandora.

“Can we build a brand score and target that more effectively and turn that into higher ROI for [advertisers], to get audio and audio personalized to work harder than TV, work harder than their outdoor ad? That’s where we’ll be shifting a lot of this focus,” Widhelm said.

Take a song like Lizzo’s Juice, for example. The Pandora person tagging the song likely would’ve labeled it uplifting, sexy, energetic and celebratory. There are, in all, more than 200 moods that Pandora scores. It takes, for example, about 30 minutes to tag a classical song.

An advertiser then could target listeners based around that mood—and a brand could (theoretically) only buy inventory along uplifting songs, for example. Pandora could also sell a specific target station centered around an activity, like driving or cooking. The service can also reach listeners on connected car and home devices, if an advertiser wants to make that request.

The offering has been live to advertisers at Pandora since this summer.

Propel, the sports beverage company, has taken advantage even though some media buyers have said they’re mixed on emotion-based advertising. Overall, buyers have said that it can be good to elevate a campaign, but it shouldn’t be the only method depended on to spread brand awareness.

Pandora created a Training Boost playlist for Propel that encouraged energetic, happy and uplifting moods for a motivational playlist. The playlist, curated with music intended to motivate listeners, included music from artists like Cardi B, Zac Brown Band and DJ Khaled. The station also included workouts one could listen to while they performed the tasks they talked you through, like stretching and circuit training.

The personalization paid off. Propel saw three times as much engagement in the station this year compared to last year. Last year, the station saw 200,000 subscribers and this year had 600,000 subscribers.

“When Propel thinks about how it defines its brand and what opportunities we really want to create for our community, we want to create joy, optimism and energy,” said Laura Barnett, senior brand director at Propel Water. “The songs Pandora was able to curate and select was an entire playlist filled with that mood.”