https://www.cnet.com/news/amazon-launches-multi-room-music-playback-for-alexa/

To get started, you'll need to open up the Alexa app and make sure each speaker has a name that's easy to remember (Amazon recommends using the room the speaker is in). Once you've done that, you'll be able to tell Alexa to play music on a specific speaker by using its name, a la "Alexa, play Beyonce in the kitchen."

Got an Echo device in every room of the house? Now, you can group them together for synchronized music playback.