AFAIK the known synth makers like Yamaha, Roland, Ensoniq, Kurzweil to name a few, after the analog period ending late 70s begin 80s, all made their own custom digital chips.
The synths I have seen from the inside, only few used standard components for waveform generation. It was their secret sauce recipe, not something you sold on the open market.
Nowadays it is all PCs with plugins, barely new hardware sees the light of day.