Voice card specs:

Single oscillator with saw, triangle and pulse output
Multiple VCAs to blend between different input signals, a main VCA for the envelope and a panning VCA for stereo output
An additional external input that can be mixed in, eg. a noise signal
One envelope generator for the VCA. It can modulate filter frequency and resonance, also with an inverted signal
A pole-mixing multimode filter with 8 filter responses:
4P LP
2P LP
4P HP
2P HP
4P BP
2P BP
3P AP + 1P LP
4P N
There are multiple options two switch and blend between different signals and filter responses
PWM, FM and synchronization inputs

https://www.tindie.com/products/27330/

Analog Voice Card for a Polyphonic Synthesizer PCB by Polykit on Tindie

PCB for a voice card used in a polyphonic synthesizer. It contains all components for a complete synthesizer like VCO, VCF, VCA and ADSR.

^Tindie