With these Max for Live devices, you can make multiple instances of a monophonic synth playable polyphonically using an Instrument Rack.
This one is free, but any single notes that are played will end up being routed to just one of your channels. Meaning if you aren't playing multiple notes at once, you will only ever hear one note at a time. https://maxforlive.com/library/device/5033/mono-to-poly
This paid solution (it's $5 for more than 4 voices, well worth it imo) gives you proper polyphonic cycling support so you can cycle between voices, meaning notes played one at a time will ring out.
4 voices for free: https://maxforlive.com/library/device/7 ... litter-2-0
16 voices for 5 bucks: https://stevieschmidt.gumroad.com/l/vKBla
If you go with the Steve Schmidt devices, you'll need to use one of these on each of your "voices" within the rack to recieve MIDI data. https://stevieschmidt.gumroad.com/l/VXabQe
Just remember to set your Corpus MIDI input to the "Post FX" input for the specific channel you're on, and everything should work.
Here's a pic of the rack setup I've been using:
![Image](https://i.imgur.com/7IvSv1i.png)