Lithophones are ancient percussion instruments made of stone, dating back to the Neolithic era

Probably someone throwing rocks at something, and instead of the normal clack-clack sound of rocks hitting other rocks, one time it went bing. And once they found out that one rock can go bing they probably started checking every rock to see if it might go bing too, or possibly bong.

I would think word of something like that would spread pretty fast, too. Like could imagine being a neolithic cave dude visiting the next village to trade some jewelry-quality bear teeth or whatever, only to see a guy playing a pile of rocks like a xylophone from the Flintstones? You'd be telling everybody about that shit. It's pretty trippy to watch now; It must have been mind-blowing back when it was first discovered. I wouldn't be surprised if it took on some kind of magical significance. And once you knew it was a thing you'd probably have your head on a swivel for the rest of your life keeping an eye out for some magic bing-bong stones of your own.

One hypothesis is that we were not hunter-gatherers all the time, but that we tried to do what we needed to do at the time we needed to do it. We hunted and gathered, but at some point we had enough to no longer need to do so. We spent the free time we gained making art and tools (as seen in the Palaeolithic art found on excavations throughout Africa, the Middle East and Mediterranean Europe). We often cut stones with harder stones and rubbed them over the surface until they took the shape that was useful to us (as seen at Lumekwi 3 in Kenya). From then on it was probably only a matter of time before we found stones that made sound.

This is all speculation and I am certainly not in a position to make any claims.

The real question is, do these rock make sounds like bells or do bells actually sound like these rocks?