Google announced at I/O that it was adding support for more streaming services as well as opening its Spotify support not just to Premium subscribers but those with free accounts, too. The latter is rolling out as Google adds support for those free users of the streaming service. To add your account, just head to the Home app and go to the Music section. You’ll find Spotify there. Just enter your login information and then you’ll be able to play music via voice commands. Here’s a complete list of the voice commands you can use.
Source: Android Police