When you start playing music on your smart display, you will see a Cast symbol in the lower left corner that shows which device the song is streaming as well. This will work with most audio apps including Spotify, Pandora and YouTube Music. Tap on the badge and you will be taken to a separate panel with all the connected speakers of your home (or Cast compatible outputs, including Chromecasts) on a list. You can tap the devices you want to play the music and use an on-screen slider to create how loud each one is. At the top of the list is a volume control that lets you quickly mute the music if it’s too loud, for example.
During a demo for Engadget, Chan Taylor played Swift’s Cardigan on a Nest Hub Max, then pulls up the list of other available assistant-enabled speakers. He tapped on two other devices to add them to the playback, and dragged their slider to adjust volume. When he dragged the volume slider to the left to soften it, the volume sliders of the selected speakers also moved accordingly. You can remove devices from grouped play by tapping the circle to the left, as you would if you disabled items in a list.
Since this control interface is visual, it is obviously not available on speakers. But if you do not have a smart display in your home, you can still use this control panel in the Home app on your Android or iOS device when it launches on these platforms later this year.
