Understanding the construction and implementation of sound cards (as examples of digital audio hardware) can be a demanding task, requiring insight into both hardware and software issues. An important step towards this goal, is the understanding of audio drivers and how they fit in the flow of execution of software instructions of the entire operating system. The contribution of this project is in providing sample open-source code, and an online tutorial [1] for a mono, capture-only, audio driver which is completely virtual; and as such, does not require any soundcard hardware. Thus, it may represent the simplest form of an audio driver under ALSA, available for introductory study; which can hopefully assist with a gradual, systematic understanding of ALSA drivers' architecture and audio drivers in general.