The QUARK software plugin is used in Digital Audio Workstations (DAWs) and similar platforms to encode four channels of discrete audio into two channels (standard stereo) audio then back four channels again, allowing the distribution of four-channel spatial recordings via widely accessible two-channel formats such as vinyl, radio, streaming video such as YouTube and music services such as iTunes and Spotify. QUARK enables musicians, filmmakers and engineers to make spatial sound work via two channel distribution formats in the Regular Matrix format then monitor audio at the pre-encode, encode and decode phases so that these creatives may mix and master spatial sound work for distribution. QUARK is based on the 1970s Sansui QS Regular Matrix format. We based most of our work on this 1974 AES whitepaper. One of the QUARK developers recently produced the first quadraphonic vinyl release in 30 years with Suzanne Ciani’s “LIVE Quadraphonic”. Work on that record is what lead to the development of QUARK. After years of research, the QS format was the best performing matrixed spacial audio format, having a strong balance between spatial accuracy both when listening to the decoded quad audio and when listening in standard two channel playback. There is also a strong community of quadraphonic enthusiasts who prefer the QS format; one of the “LIVE Quadraphonic” collaborators Involve Audio even produces an incredible modern hardware decoder called the Surround Master. One of the most surprising discoveries is that the Dolby Pro Logic II (DLP2) format is very closely modeled after the Regular Matrix format. DLP2 is nearly universally installed in nearly every surround sound capable receiver/processor since 2001.