In other cases, please refer to the instructions specific to your host operating system to configure sound. Several sound cards are not supported by Linux. If you have one of them, you will not be able to play sound in the virtual machine, even if the guest operating system supports that card. In this case the virtual machine will have a virtual sound device, but you won't hear anything. You must quit that program first.
Virtual machines can share the sound device.
If another virtual machine is currently using it, simply terminate the application that is producing sound. Only one virtual machine at a time can actively use the device. At power on, the device must be unused. Enlightment Sound Daemon is running and using the sound device. You can use the ESD's esddsp wrapper to start the Workstation virtual machine's configured for sound.