I have been interested in this subject most of my audiophile life. Decades ago I heard a demonstration of a Yamaha DSP-1 Sound Field Processor and I was blown away. Since then I have acquired several processors including a Carver C-9 Holographic Generator, BSG QOL, Black Ice Foz SSX, and a DSP-1. Someday I expect to write a review of these processors in case anyone else is interested. I have not heard the BACCH system but I look forward to it. I've got a spare MAC laptop that I could use but I would like to hear it at an Audio Show if possible.
For now I'll discuss the BSG QOL processor because it's my favorite and there is good reporting on it. The unit is very good at expanding depth of the soundstage. You can almost see the instruments placed in 3 dimensions with much more depth than standard stereo. I really like it and I run it most of the time. Whenever I compare components I bypass it because it makes everything sound better. I like it so much that I bought a spare in case this one breaks.
There are several good articles in the trade mags about this processor and they go into the theory behind it. If you are interested you can learn more about this subject in layman's terms. Here are a couple links: Stereophile BSG and TAS BSG Review