The CZ-1000 is a polyphonic, fully digital, first generation synthesizer from 1985 with the Casio-specific phase distortion synthesis, which had already been used one year before in the popular CZ-101. Both devices share exactly the same inner workings, only differing by size and casing, with the CZ-1000 being available at much cheaper prices.
The Casio CZ series offers sounds similar to those of the FM synthesis devices by Yamaha, a bit more analog and dirty, though. The Casio CZs are also constructed in a much neater and understandable way. I built 2 soundchip-manipulating switches into mine - they produce hard 8-bit sounds and can also evoke random parameter changes