Almost 40 million people now pay to listen to Apple Music. That’s not bad for a service that was met with skepticism when it debuted back in 2015.

Apple Music still faces strong competition from Spotify and Google Play Music, but it’s growing strongly. And all those people putting down $9.99 a month adds significantly to Apple revenue as streaming services have become the top way to listen to music.

Senior VP Eddy Coe announced this afternoon that Apple Music had surpassed the 38 million mark at the SXSW festival, according to Reuters. The service had about 36 million subscribers just last month, 30 mil. in September, and 27 mil. in June. That’s 9 million new subscribers in about nine months.

Apple Music vs. Spotify

Top rival Spotify boasted 71 million premium subscribers at the end of last year, so it’s nearly twice as big as Apple. Back in mid-2015, when Apple Music debuted, Spotify had 15 million subscribers, so it’s grown faster over the past 2.5 years.

Those are global figures however, and the situation is different in the U.S. Apple Music has reportedly been growing 5 percent every month as compared to Spotify’s monthly growth rate of just 2 percent. And Apple could become the top music streaming service in the U.S. as early as this summer.

The bottom line

Apple Music became necessary a few years ago when purchases from iTunes began to drop off. People preferred music subscription services to buying individual tracks or albums, and Apple followed its customers.

The exact revenue from its streaming music isn’t reported by Apple each quarter. Instead, it’s combined with income from other services like the App Store, so there’s no way to know just how much the company is pulling in. Still, revenue from that sector was up 18% year-over-year last quarter, which is surely a reflection of the growing number of Apple Music subscribers.