I find good idea to build a rack for my synth korg m1. This synth have 4 individual outputs and i think is interesting that synth M1 with this classic sounds can have more parameters. I read many times how to build a rack but for me it’s difficult as I had every synth and drum machine separate on my studio. So anyone can help me to build a idea for a rack have “ tools” like filters , parameters, effects for the 4 outputs of this synth.
Thanks Andreas

Basically, what you need is simply a single module: an input preamp. At least, if all you plan to use the modular for is processing. If you want to control the modular with the M1, then you'll need a MIDI-CV conversion module as well. As for whatever goes in between those, that'll depend on what you're trying to do with the build overall.

However, one thing I'd also like to point out is that if you have all of these synths and drum machines, you really should consider treating THEM as "modules" as well, routing all of their I/Os to a central patchbay. I've used this working method for over 25 years now, and it massively speeds up the interconnection process between devices.

another thing to consider is that a 'modular effects rack' is effectively a full blown modular synthesizer, with the sound sources replaced by external ones - which generally means you need an input module of some kind to import the sound sources

this means that modulation and utilities are just as important in an effects rack as in a regular synth - don't skimp on the most important stuff (modulation and utilities)

Thanks both for your replays. I want to build a rack only for this special synth and only. Your infos help me to think and now I visualize that the 4 out of the M1 goes in 4 individual inputs on rack from then I can have like 4 filters for every channel?or 4 delays for ever channel? This is the only thing I didn’t understand. Thanks

Or you could sum the four outputs down to either stereo or mono, and feed it through a stereo filter (like the Morgasmatron or the Dual Borg) or any mono VCF you prefer. Even better, if you want to keep the outputs totally separate, you could even go with several different filters for coloring each output differently. Lots of possible options there...