Other than that, though, this is macOS High Sierra, running smoothly in VirtualBox. The only thing not working is sound, which for some reason is highly distorted or nonexistent. Some of the folks at the InsanelyMac forums have figured out a process that works. We haven’t yet tested it ourselves, but we’ve heard good things. It promises to take you through the process of installing and setting up a macOS virtual machine. If you want to install a newer version of macOS in VirtualBox, check out this script on GitHub.
Update: The instructions here apply to older versions of macOS.