not attempting replication Piston Honda or E370...
was merely researching those manuals
took so long yet have wave "index" modulating partials
sort of suspect piston and e370 are using wavetable DCO chips
(sort of like like for instance Electric Druids's VCDO)
https://electricdruid.net/product/vcdo-wavetable-oscillator/then merely doing VCA X Mix Between chips
his DCVO was originally "Open Source" at one time for modifying/burning code on chips
could be completely wrong
yet merely saying some methods that popped in my head for prototyping hardware module
yet that is wavetable of 16 & 8 subs @ 8bit
prototyping in software so actually have good grasp of wave morphing
Bjorked up recently batches of waves in AudioTerm
because forgot step of re-synthesis with root pitch
anyways guess need going back for doing that
actually have been using PPG waves for source mutating
didn't realize what they were anymore because not marked accordingly
anyways
the morphing engine is working in transwave style/index modulation & X mix between wave banks plus modulating sample banks