Having seen some 3d printed capos, which tended to not clamp down hard enough to be effective, it struck me that a similar idea might work very well to hold a piece of material against the strings and dampen unnecessary ringing. As someone with several stringed instruments on the wall, I find the ringing irritating when practising or trying to record. I have used strips of foam under the strings but this is a more elegant and longer lasting solution. Additionally, the cloth can be used to wipe down the neck before rehanging.

Use the provided OpenSCAD file to fine tune for your instruments.