Amazon grew its Music Unlimited streaming service by more than 70% in the past year, according to data by Midia Research published by the Financial Times. The service currently has approximately 32 million subscribers. However, the report didn't clarify whether that includes trial subscriptions as well as paid ones.

Amazon Unlimited Music is still smaller than its biggest competitors. Apple services head Eddie Cue recently revealed that Apple Music has about 60 million subscribers. Spotify has more than 100 million. Google has offered a variety of streaming services via YouTube that it has shuttered, rebranded, and shuffled around, making it difficult to quantify the company's traction with music listeners. In any case, Amazon still has a lot of catching up to do.

Midia Research credits the rapid growth of Amazon Unlimited Music to the proliferation of Amazon Echo smart speakers and other devices with Alexa. While these devices can play music from other services like Spotify, they default to Amazon services in many cases. For example, if you ask Alexa to play David Bowie's "Heroes" on a Sonos One speaker, Amazon's streaming music service will be used. You have to say "Play David Bowie's 'Heroes' on Spotify" to get a different result.

According to an eMarketer report, Amazon accounted for about 67% of all smart speaker sales in the United States in 2018. And that's a big pie to take a slice of: more than a quarter of US adults had bought a smart speaker as of earlier this year.

Commenting on the story, Amazon Music VP Steve Boom said, "We're not battling for the same customers as everyone else... For the industry to reach its full potential, we can't just look at 15- to 22-year-olds." To that point, Midia Research's data showed that Amazon's service skews slightly older, with 14% of its users over the age of 55, compared to just 4% for Spotify.

Fast growth for Amazon now doesn't necessarily suggest the service is more attractive than those of rivals, though. Spotify and Apple Music have been on the market much longer, and brands tend to see diminishing returns on marketing investment as they saturate the market over time. It's also worth noting that Amazon Music Unlimited is cheaper than most rival services. That's especially true if you have Amazon Prime (it's only $8 per month for Prime subscribers) or if you only use an Amazon smart speaker to listen ($4 per month), which may also help the service grow.