I added two quarter-inch jacks to the rear of my MKS80.
External audio can replace the noise waveform on VCO 2
Much fun ensues.
Note that my MKS80 has the multi-mode filter boards installed.
https://youtu.be/_rMFmmRVPWQ?si=v5XEdzYie56m0ND3
Finalising those for production atm.