First he played it at normal speed. The normal speed play back was muffled, dull, and not interesting. This experience motivated me to quickly build a seismometer using a 20-pound junk power transformer as the weight. The resulting instrument was much more sensitive than I ever expected. I was able to easily see deflections of several centimeters at times, and especially when a series of underground atomic bomb tests were being conducted hundreds of miles away in Nevada.
All options are interesting and well worth seeing and hearing.
Both types of recordings can be signal processed in many ways at playback.