I guess you are not asking for the schematics
The architecture is quite straight forward and has just the same logic as the instrument layout.
Audio-signal flow is:
- two single voice built a pair -->
- two pairs built a group -->
- two groups are all the 8 voices -->
- Mod-Delay -->
- Drive -->
and then we have all the modulation options (buttons, switches, feedbacks etc.) as shown on the user interface. The manual describes pretty good, how everything is hooked up and how it works in general. But it’s up to the user to explore the very different possibilities.
Example: The FM is not as usual - compared to a “complex oscillator”. There is a kind of modulation of frequencies, but with very surprising behaviour.
You can download some files, including blank patch-sheets. They represent exactly, what is going on under the hood and how the voices, pair of voices, groups of 4 voices etc. can be used from a single voice to groups modulated by FM or Feedback.
https://somasynths.com/lyra-organismic-synthesizer/ (download the manual)
https://somasynths.com/lyra-8-presets/ (download patch sheets etc.)
I don’t think that imitating the Lyra with any kind of digital gear has even got a tiny chance of success, if the circuits are not simulated like it’s done for the Roland Aira series.
The Lyra sound is generated by many crossmodulations of the circuit board itself, not only by the position of the visible switches or Mod-buttons. Put all modulations to neutral, change the pitch poties or the envelopes and there is more to hear than expected.
Even if a switch is in FM position and the Mod-Button is down to zero, there is already significant frequency modulation. Even the oscillators of one pair see each other and crossmodulate. Many of the typical sounds possible are generated by the various feedback options, which are - as I suppose - planned and unplanned by the designer.
Last but not least … there is the opertional aspect. The Lyra seems not to be designed to be used as a keyboard like instrument. The most interesting results are achieved, if we keep flipping switches, moving knobs, tuning/detuning and so forth … I train this with both hands and more then three fingers in action. That interface is an essential part of the game