@Mlie So I took a look at the mod file and then looked up pianos online, and I noticed that pianos don't typically have silver or gold in them. I don't see why they couldn't be made of silver and the like, but seems like historically they are just made of metal(steel) and wood. However, there seems be be a larger variety of wood they can be made of compared to a variety of metals, so I plan on changing the cost list to have an increased steel base cost(from 30 to, say, 80) and simply make it so the regular wood requirement isn't inherently there. Adding to this, I'll have the stuffCategories be both woody and metallic instead of just metallic and keep the stuffcostcount amount be 100. This way it'll still cost the same units of materials(currently it's 50 wood, 30 steel, and 100 stuff, adding up to 180) and allow it to be made from both wood and metal stuff. This means that it will be made of 80 steal and then 100 of any metal or wood(so, a steel piano would be made of purely 180 steel and nothing else, which doesn't seem quite right to have piano keys be made of just steel, but not much else I can do).

Originally I considered making it so it was just made of woody stuff, but I noticed that items that make use of multiple stuffs work just fine(such as a club being able to be made out of wood, metal, and stone) and I liked the idea of a piano being made of just pure silver(so 80 steel and 1000 silver. I'll admit, 1080 units is a bit annoying, though. 1100 looks better...). Alternatively, I also considered making it so a piano required an additional base cost of 20 silver to round it all to 200, but then I realized that 20 silver seems a bit too insignificant, not to mention it would then be impossible for anyone to build the piano if they have no silver on hand and no traders coming by to buy their stuff(typically this isn't an issue, but you never know). To go even further, I also considered making stony a part of the stuffCategories so one could make a marble piano, but wasn't too sure about this.

I'm not too familiar with modding(but I know a bit of code) so this may take some trial and error on my part. As such, I've yet to change anything in the def files and thus I haven't tested anything yet, but I wanted to know your thoughts. Is making the stuffCategories have woody and stony in edition to metallic a good idea? Is there something else I can do to the base cost to make it better/make more sense? Should I add the additional 20 silver base cost? Anything else that comes to mind that I should take into consideration? Any input would be appreciated.

Edit: I tested it out and it seems to work. I didn't add the 20 silver, but having it be a base cost of 80 steel and then 100 "stuff" worked just fine. I did encounter a bit of a bug during the test, where the blueprint once it's is worked on(not the see-through part, but when work starts it has those corners that show it's being worked on) shrunk from 3 blocks wide to 1 block wide. Once it was built it "looked" just fine, being 1x3 in size, but I noticed that the side of the piano can be walked through while the center could not. Furthermore, it could be build and installed in such a way where the sides of the piano will clip into other objects. I'm not sure if this is an issue with the mod itself or something that happened due to my meddling. I'll undo my changes and test it out again.

Edit 2: Looks like it's the base mod that makes the edges walkthrough and clip into other structures. If that was intentional then no worries, but I personally think that the piano shouldn't be walkthroughable on the edges like that, or at the least it shouldn't clip through other items. I don't even know where I'd change that for my own personal use, but I can just ignore it and just make sure that I position it so that it doesn't clip into it.

...now that I think about it, I wonder if I could put a lamp on the sides so it looks like the lamp is sitting on the piano. On second thought, I don't think that should be changed. Gonna test putting a lamp on top. :D So unfortunately other items clip through the piano in unappealing ways. As such, the lamp on top of the piano idea doesn't seem to work very well.