Amazon.com on Wednesday launched a music streaming service with subscriptions as low as $3.99 per month for owners of its Amazon Echo speaker, the latest entry in an increasingly crowded field. Amazon Music Unlimited is being positioned to compete against existing services such as Spotify and Apple Music. It will cost $8 per month, or $80 a year, for members of Amazon's $99-a-year Prime loyalty program. Non-Prime members will pay $10 a month, the same monthly fee charged by Spotify and Apple Music.

Owners of Amazon's Echo smart speaker, meanwhile, will be able to get the unlimited music service on one device for $4 per month.

The steaming service is one more perk - like two-day free shipping and Amazon Video - that Amazon hopes will attract people to its Prime program and thus encourage them to spend more on its flagship site. Amazon already offers Amazon Prime Music for free to Prime members, but that includes about two million songs, while the new service boasts a catalog of "tens of millions" of songs.

Amazon is hoping to stand out is with its Alexa voice control, via the Echo or other Alexa-enabled devices. Users can ask the Echo to play a certain song or playlist, but can also search for music just by saying they want to hear the "new" song by any artist, a genre of music from a certain decade, or by saying the lyrics of a song if they can't remember the name.

The service is available starting Wednesday in the U.S. and in the U.K., Germany and Austria this year.