Apple on Monday released an update to macOS High Sierra. The update comes on the heels of iO 11.4.1, watchOS 4.3.2, and tvOS 11.4.1, which were released earlier in the day.
AirPlay users will want to install this update sooner than later. MacOS High Sierra 10.13.6 includes AirPlay 2 multi-room support, so you can now play music on multiple AirPlay 2 speakers and control them on the Mac.
According to the release notes, the 10.13.6 update also: