On another world, there is giant ravine leading into a cave where a sentient species live (Let's call them Cavers). They have limited access to materials; the only resources they have are rocks, metal and sometimes unfortunate animals that fall into the ravine.

The Cavers have made drum and xylophone-like instruments, smelting out the iron from the rocks around them and hollowing out the iron to be hollow with a specialized drill-like tool. Occasionally when an animal falls down from the surface, musicians may collect the pelt and use it as a leather covering for their drums, making the sound richer.

The most recognizable instrument invented by the Cavers is a mix between a water mill and a music box. A huge metal comb sits next to a giant cylinder, which is turned by an underground flow of fresh water. The pins on the cylinder continually play the Caver anthem, to the point where most Cavers have accepted it as background noise.

Is all this possible to do in real life? If not, what should I change?

  • $\begingroup$ I don't see why that wouldn't be possible. Most music boxes are just run by a spring, so replacing the spring with another drive mech isn't a real issue. Making it large shouldn't either. $\endgroup$ Jan 4, 2018 at 22:05
  • $\begingroup$ The vibration frequency of a blade depends on the material and on the dimensions of the blade. I cannot imagine a "huge" metal blade vibrating at audible frequencies. You may want to consider a water-powered pipe organ or a carillon combined with a mechanism similar to a player piano. $\endgroup$
    – AlexP
    Jan 4, 2018 at 22:31
  • 1
    $\begingroup$ Conceptually you have created a much larger version of this: youtube.com/watch?v=IvUU8joBb1Q $\endgroup$
    – Thucydides
    Jan 5, 2018 at 1:15
  • $\begingroup$ Not just possible, it's been done: en.wikipedia.org/wiki/Water_organ $\endgroup$
    – jamesqf
    Jan 5, 2018 at 4:17
  • $\begingroup$ I would definitely consider making this a percussion instrument rather than a plucked one. Drums, bells or xylophone... Keys? $\endgroup$
    – bendl
    Jan 5, 2018 at 13:01

2 Answers 2


Nothing you describe is particularly hard except for this:

hollowing out the iron to be hollow with a specialized drill-like tool.

Spinning a drill-bit takes a lot of force, particularly one large enough to be a drum. I can't imagine a primitive society having the materials to do drill on that scale - it simply requires an unbelievable amount of force. Some sort of forging would be far far easier. Humans have been making cauldrons using casting for centuries.

As for the water-wheel powered music box? Nothing hard there at all. The tines would have to be some fairly stiff steel though. However, cou can't make a nice "plucked" instrument with cast iron, although you could do bells. Of course, you do have the materials to make steel (iron + carbon), so if your industry is up for it then you could make a typical music box. Making it water powered is not hard at all.

Finally, Larger = easier to make, although it also means lower pitched. I'd be fascinated to hear what a gigantic music box sounds like.

  • $\begingroup$ Alright, I'll take notes on that, especially the part about forging. Thank you! $\endgroup$ Jan 5, 2018 at 21:11

What do they burn to smelt the iron?

My biggest question is how they smelt. In real life, wood was the only material for burning until the Common Era, and alternative fuels like coal didn't really take off until the Early Modern period (despite earlier use in China).

I imagine there isn't much wood in a cave, so the Cavers would need to burn coal to smelt iron. That isn't really impossible, it just has to be considered that they need a coal mine nearby.

Does it have to be iron?

Iron is much harder to work than bronze. Furthermore, you won't find many modern musical instruments made of iron or steel. Trumpets and horns are made from brass, and alloy of copper and zinc, which is in any case much easier to melt and work with than iron. It would seem likely that the Cavers, especially if they are generally technologically primitive, would make their equipment of copper and brass.

You will still need something to burn to smelt copper and brass, so the coal is still necessary, but you need a lot less of it due to lower melting points.

Drilling though metal is hard

Drilling through iron is very hard; fortunately copper and brass are easier. The easiest way to do this would be to invent gearing. Brass (or preferably bronze; copper plus tin) gears won't last a long time, but they will allow you to make some useful power applications. You can gear a lathe to your water mill and spin it at high speeds. This is one of the only practical ways you can get your Cavers to bore holes in metal. However, metal gearing of this precise nature wasn't really utilized until the 1700s, so this technology is somewhat out of place.


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