The Parallels Audio Controller (9X) is a virtual audio device used in Parallels Desktop, a popular virtualization software that allows users to run Windows (or other operating systems) on macOS, Linux, or other host systems. When you use Parallels Desktop to run a Windows virtual machine (VM), the software often emulates various hardware components, including an audio controller, which enables sound functionality within the VM.

The "9X" designation likely refers to compatibility with older Windows versions (such as Windows 95, Windows 98, or possibly Windows ME) that were commonly used in virtual machines when Parallels was initially developed.