https://techcrunch.com/2017/08/29/you-can-now-play-your-music-across-multiple-echo-devices/

Amazon this morning announced a new feature for its Echo devices called “multi-room music,” which allows owners with more than one Echo to control where their music is played, or even sync it across a group of Echo devices using voice commands. For example, you’ll be able to tell Alexa to play your music in the living room, play music upstairs or downstairs, or even just play your music everywhere.

Beyond just saying “play my music,” followed by a location, you can also ask Alexa to play your favorite artist, or other music-related commands, as you would normally.