[Photo credit: Amazon.com]

As if the music streaming war wasn't already complicated—Amazon has now become a major player in the game with its new service: Amazon Music Unlimited (via the New York Times).

The major difference between Amazon Music Unlimited and Amazon Prime Music is the catalog of songs. Unlike Prime's two million songs, Unlimited will offer a catalog like that of Spotify and Apple Music, with tens of millions of songs.

Read more: Spotify outpaces Apple Music, reaches 40 million paid subscribers

However, it's the price of Amazon Music Unlimited that's turning heads. At just $3.99 a month, Amazon Music Unlimited is severely undercutting its competition—but there is a catch. The catch is the Echo.

That $3.99 monthly price only works when you pair Amazon Music Unlimited with the Echo, Amazon's voice-activated speaker system. For Amazon Music Unlimited to work with your phone and laptop, you need to opt-in for a $9.99 monthly charge ($7.99 for Prime owners).

Read more: Spotify and Tinder partner to share your music with virtual love interests

There's plenty of perks that come with pairing Amazon Music Unlimited and Echo. The most prominent is Alexa—a voice assistant that will cater to all your music listening needs. Simply say to the Echo, "Alexa, play the new Green Day album," and Revolution Radio will start playing.

Other streaming services, such as Spotify and iHeart Radio, also work with the Echo, but there are features that are exclusive to Amazon Music Unlimited. The coolest feature is the ability to search through lyrics. For example, a user can say, "Alexa, play that song that goes 'so long and goodnight'," and it should, theoretically, play "Helena (So Long & Goodnight)" by My Chemical Romance.

Let us know if you're interested in Amazon Music Unlimited in the comments.