[Kaliv]

The confusion might be between what you call damage. The harp of a piano is pretty good solid metal. Less tension on it won't do anything to it. There is usually a thick piece of wood that the harp attaches to...if that splits (like mine), you may never be able to bring it back up to it's true tune. But that damage was cause by the prior owners not taking care of humidity and such, not whether or not they tuned it. But here's the real deal...if you haven't tuned the piano in a while, the chance that they may break increases. Adding strings to a piano isn't necessarily cheap, and usually requires a series of frequent tunings once the new strings are added.