It seems to me that an instrument that uses tuned mettal bars like a Glockenspiel should be incredible resilient. As long as it is protected from rust it should

It seems to me that an instrument that uses tuned mettal bars like a Glockenspiel should be incredible resilient. As long as it is protected from rust it should stay in tune basicly forever. Also packs super small. If you are after something more Piano like then a Celesta would be a good bet, it’s basically a cross between a Piano and a Glockenspiel. https://en.m.wikipedia.org/wiki/Celesta https://en.m.wikipedia.org/wiki/Celesta Do not dismiss a normal piano though, a steal frame piano should stay in tune for a considerable time under stable temperature and low humidity. Should be achievable in a bunker.