Seismic is surprisingly intuitive and fun to use and might even be underrated.

I have used hardware synths and so am less interested in emulation and more in more unique sounds and how they can 'reproduce' and evolve over time. (In this regard perhaps, Zebralette's nice too but I'm kind of bugged that it's apparently a deliberately-limited version of Zebra 2. I also resent other forms of this/similar kind/s of synthesis that seem to be deliberately limited. Yes, I am anti-crony-capitalist.).

I'd put an extra star for Seismic if it weren't for a bug which is when I open a saved sound, the waveforms appear wrong, even though the sound is correct if I recall. (I am using Ardour 5.12 64-bit on Windoze 7.).

To Seismic's creator, I have been toying with the idea of creating in a 3D program Seismic's GUI if you might be interested in collaborating in this regard. No guarantees, it would depend on time and opportunity, but let me know and maybe we can work something out. Full bucket Music seems to have nice GUI's yes? Or maybe others? In any case, Seismic looks fine as-is, and its 3D-ification could still honour its particular look and outlay, etc..