Update: none of the 1977 sound files would run properly muxed into the video - they’d all run on the PS4 for a few moments with choppy AV, then cut out into a “cannot play the media” message that I received before. I hit closer with the Laserdisc audio muxed into the video, at least in that it never cut out on me completely. It was still akin to playing a scratched DVD, so it warrants more experimentation. I’d download the programs I need to convert the files for use on my PS3, but my lappy is work-provided, and most programs require admin approval for installation. Frankly, I was surprised mkvmerge was able to run without a hitch. Work in progress.