When did they stop making pianos with ivory keys?
Piano keys never were made entirely of ivory – there was a very thin veneer of ivory glued onto a piece of wood. In the 1950s, the makers of pianos stopped using ivory because it was getting harder to come by, more expensive, and the demand for pianos and other keyboard instruments meant that the supply was insufficient. At about that time, there was concern expressed about killing off elephants for their tusks and, serendipitously, plastics had evolved to the point where they were now better than genuine ivory – they were easier to work with, didn’t discolor as ivory did, and could be attached more firmly to the wooden key.