Amazon’s Alexa supports the Multi-room Audio feature that helps the users to stream music over multiple speakers at the same time. This feature lets you play music from Amazon Music, TuneIn, iHeartRadio, Pandora, Spotify, Sirius XM, Apple Music. To listen to more than one stream over different speakers simultaneously, you have to use the Amazon Unlimited Family Plan. To know how to set up multi-room music on Alexa, refer to the step-by-step guidelines mentioned on this web page.
If you have not installed the Alexa application on your smartphone yet, install it as per the instructions given here.