Microphones in all horizontal directions and two in the vertical, hung by a wire from the ceiling of a venue. We recorded the results using an Alesis ADAT 8-track multitrack (swapping VHS tapes was my very important job.) The "secret sauce" was some kind of binaural post-processing that allowed you to hear all three dimensions through a horizontal array of speakers, but I never got into those details.

The goal was ultimately to stream extremely high-quality concert audio to the home: people felt that stereo and even 5.1 was too restrictive. This was in the early days when everyone was trying to find killer apps for high-bandwidth broadband connections, so sure, why not.

ETA-- Another memorable experience in this project was playing the Woodstock tapes for Jimmy Buffett when he flew his seaplane in to check out the technology. We were very careful to point out that you could hear the drum circle :)