You can use the Google Home app to group speakers for synchronous music throughout your home.

Make sure that your mobile phone is connected to the same Wi-Fi network as your speakers.

To group speakers:

1.     Open the Google Home app .

2.     Tap Add  > Create speaker group.

3.     Tap each device you want to include in the group.

4.     Enter a name for the group.

5.     Tap Save.

You can learn more about using Chromecast built-in at support.google.com/chromecast.