One of my instruments has felts in the finger buttons (underside) to provide a soft landing for the buttons when depressed. After all, that metal-to-metal sound is distracting after a while. I know there are places to order felts, but I want to experiment here a bit.
What are some good options for hardware / arts & crafts store-sourced materials that can do this job? Since I'm experimenting I don't know the thickness I need and will probably want to procure a few different thickness. I would think density, thickness, and composition of material would all matter.