“Why does a harpsichord go out of tune?”
Australian harpsichord maker Carey Beebe answers an age-old question. (Follow the link below for more details.)
The harpsichord as an instrument has a largely undeserved reputation of requiring too-frequent tuning. Even other excellent instrumentalists have formed this opinion from bad experiences, usually with poor harpsichords. A good harpsichord, though, kept in stable surroundings, will stay in decent tune a surprizing time—perhaps even weeks. All instruments are subject to the vagaries of their environment.
Much more: Why does a harpsichord go out of tune? (Carey Beebe)