Phil Ciricco recently documented his restoration/rebuilding of a 1938 Novachord. The novachord is an early, polyphonic keyboard made by the same company that made its more famous cousin, the Hammond Organ. From his description, it was a long, difficult project, but you can hear how well it turned out from the audio samples at the bottom of the page. It makes an incredible range of sounds, some very warm, some rather dark, and others reminiscent of the soundtracks from early video games. (via).
Here is an example of what it sounds like, overlaid onto footage of the 1939-1940 World’s Fair, where it was introduced.