YouTube Music doesn’t have an audio-only toggle in the web-based version like the mobile app, but you can minimize the video, and close the mini player to keep listening to the audio in some tracks.

The arrow icon on the bottom-right will turn upwards when you minimize the video.

This will close the mini video player, and continue playing the track in audio only. When you hover over the “X” icon and wait a bit, it’ll say “Close mini player” on a pop-up label. This is a premium feature, and only available with a paid subscription to YouTube Music premium service. You won’t see it without a paid YouTube Music subscription. This feature may not be supported in all videos.

This will close the mini video player, and continue playing the track in audio only. When you hover over the “X” icon and wait a bit, it’ll say “Close mini player” on a pop-up label. This is a premium feature, and only available with a paid subscription to YouTube Music premium service. You won’t see it without a paid YouTube Music subscription. This feature may not be supported in all videos.