CASIO CTK-1000 uses IXA (Integrated X-Sound Architecture) synthesis engine.
According to CASIO's advertisement, IXA is a 'newly developed' PCM / Nonlinear hybrid synthesis.
No further information has been found to this day.
CASIO CTK-1000 (1993)
Though it looks like just a Casiotone, it can create new sounds never heard before.
Here are some sound examples of CTK-1000's IXA engine, and some hypotheses about what IXA actually is.
Please tell me any information about CTK-1000 and IXA.