Hip-hop. R&B. Jazz. For decades, we've used these categories to describe different styles of music and, just as important, our own tastes and musical identities. But increasingly, music listeners are shifting away from these genre labels, according to Spotify. What they really want is a set of tunes to fit their mood.

It took Spotify a great deal of testing and data-crunching to arrive at that revelation. And it isn't stopping there. It's taking what it's gleaned from millions of users' listening habits to craft a new kind of song entirely: One that intensifies along with your running workout, matching its beats to your precise pace. When you speed up, it speeds up. When you slow down, it does, too.

Driven by mounting competitive pressure from the likes of Apple Music, Spotify is searching for new ways of hooking fans. If this crazy experiment takes off — and Spotify admits it might not — it could change how many of us, from athletes to scientists, think about exercise.

When Spotify began mixing its own playlists and tagging them ("Focus" for people who needed music to work to, or "Dinnertime Acoustic" for unwinding) it noticed a big uptick in interest, particularly when mood-based playlists were displayed right beside a traditional genre, according to Mark Silverstein, Spotify's head of product, tech and policy. Mood-based playlists aren't just different collections of songs; in the case of Spotify's commuting playlists, the company will occasionally mix in news, weather reports, even audio clips of Jimmy Fallon for some comedic diversity.

As a result, fewer people began selecting genre playlists, and many more began opting for the mood-based playlists. And that carried over into the playlists people were making for themselves.

"People were not creating the ''90s hip-hop' playlist, they were creating 'my running playlist' or 'my cooking playlist,' " said Silverstein Tuesday, at a conference hosted by the Technology Policy Institute in Aspen, Colo.

That prompted Spotify to begin thinking about running more closely. For years, scientists have theorized about a link between music and exercise. One 2007 study suggested that fast, loud music was associated with faster running speeds and an increased heart rate. Another found in 2011 that music helped triathlon runners stave off exhaustion and run nearly 20 percent longer than their peers who ran in silence.

Silverstein said Spotify conducted its own research with Nike and Olympic runners. And it found that at higher beats per minute (BPM), music did appear to have a positive effect on workout performance. The data convinced Spotify to set up a new feature in its app that lets users set a BPM filter. If you set the filter at 180 BPM, for instance, the company will only stream songs that match or exceed that number. The idea has proven immensely popular among runners, said Silverstein.

But Spotify soon learned that it didn't have enough songs in its library at really high BPMs. It couldn't satisfy listeners' demands. So it turned to DJs and orchestras to create entirely new tracks that are tied to your pace. Silverstein didn't elaborate on the software behind this feature, but what may be happening is that the songs respond to your smartphone's accelerometer, tracking the bobbing of your body as you run.

"We've created a completely new music format," said Silverstein. Whether it proves popular "remains to be seen," he conceded, but Spotify clearly hopes it's stumbled on a new formula to keep users coming back.

Runners and cyclists have long been able to track their workouts in terms of steps taken, calories burned and elevation gained. Together with the latest apps and wearable devices, data has given us a whole new way to experience exercise.

Now, data won't just be what comes out of your run. It'll be what improves it.