One of the things I had the most trouble wrapping my head around w/ the MS-20 is what modulation effects what.
If you want to use the A4 to modulate the filters, for example, there’s two ways to do it. You can patch something into the “Total” jack (top right corner) and dialing in the modulation intensity using the three “MG/T.Ext” knobs. Or, if you want to control them individually then you patch into the individual patch points and use the “EG2/EXT” knobs.
If you want to control volume, patch into the Initial Gain jack… but honestly that thing’s real screwey and I’ve never figured that bit out too well.
This dude has a whole bunch of experimental noisy MS-20 stuff that you can probably bring an A4 to:
https://www.youtube.com/channel/UCq-Ezi8YguBOI1RKYUch28w
The MS-20 is a real, real weird beast. Fun as hell especially with other CV gear, but definitely weird.