The service is even cheaper if you own an Echo speaker. Amazon has a $4-per-month tier, dubbed "For Echo," which gives you full access to the service on one Echo, Echo Dot or Amazon Tap device. The company says "tens of millions of songs" are part of its catalogue, including over two million that were already available on Prime Music, but it did not share specific numbers when asked. That said, Director of Amazon Music Ryan Redington tells Engadget that all three major labels are onboard -- Sony, Universal and Warner.

As part of the launch, Amazon redesigned its Music app for iOS, Android, desktop and Fire products from the ground up. Not only will it work for both Prime Music and Music Unlimited users (including offline), but Redington tells Engadget that every aspect of the application has been tweaked to be simpler and easier to navigate. However, the most important part about Music Unlimited, he notes, is the integration with Alexa and Echo devices. For example, you can say things like, "Alexa, play the song of the day?" or "Alexa, play Greenday's latest album?"

What's more, Redington says Alexa is capable of playing tracks based on your mood, as well as tell you who sings a song even if you only know part of the lyrics. I was given a demo of these features and they worked seamlessly, but that's not really surprising since Alexa has an excellent reputation as a virtual assistant. Redington claims Alexa will keep getting better with time too, as it learns more about your listening habits through Amazon Music Unlimited.

For Prime members, Amazon Music Unlimited seems to be a no brainer, namely because it only costs $8 per month. Apple Music and Spotify, for reference, are $10 each for a regular, non-student account. That said, it might be hard for people who already have a streaming sub elsewhere to jump ship -- building a whole new library and set of playlists would be a tedious process.

Music Unlimited is only available for US customers right now, but the company says it "will continue to expand and enhance" the service. For starters, it's expected to launch in the UK, Germany and Austria later this year, though Amazon wasn't clear on the exact time frame. A family plan is also going to be available soon, which will allow up to six people to stream music simultaneously for $15 monthly.

According to Redington, the long-rumored service was part of Amazon's business strategy since the launch of Prime Music in 2014. Still, it wasn't until this year that his team actually went all in on the idea, with the goal being to develop a "fun and engaging" product. And with Alexa and Echo in people's homes now, he says, it felt like the natural time to introduce Music Unlimited. It sounds like a good start, but we'll see if listeners are willing to give it a chance in the crowded music-streaming space.