Midicake ARP has 4 MIDI output channels so why not run a Eurorack modular rack with 4 separate voices?
Here’s a list of 4-Channel MIDI to CV converters that might work for you.
Prices are in GBP and include shipping and calculated customs tax into the UK (where applicable).
https://www.endorphin.es/modules/p/shuttle-control - £435
4 channels - Clock exclusive - 12hp - MIDI DIN/USB/2x USB Host
https://six4pix.net/product/cvocd - £150
4 channels - clock exclusive - Not Eurorack - DIN/TRS
https://majella-audio.com/shop/mcvc-midi-to-cv-converter-diy - £215
4 channels - clock inclusive - 14hp - DIN
https://www.hexinverter.net/mutant-brain - £180
4 channels - clock exclusive - 8hp - DIN
https://doepfer.de/a1905.htm - £270
4 channels - no clock - 16hp - DIN/USB
https://afterlateraudio.com/collections/midi-cv/products/threads-1u - £219
4 channels (no velocity) - 1U format - TRS/intellijel
https://www.signalsounds.com/flame-uqmcv-eurorack-midi-to-cv-convertor-module - £163
4 channel - clock inclusive + thru - 6hp - TRS
https://michigansynthworks.com/products/mbrane-6hp-yarns - £218
4 channels (no velocity) - no clock - 6hp - TRS
Mutable Instruments Yarns Discontinued - £270ish on Ebay
There’s a good article on this topic here: - https://www.perfectcircuit.com/signal/midi-to-cv
Two others to add to the list are the Bastl 1983 (MIDI to 4 channels of CV) and the new Befaco MIDI Thing v2.
And two eurorack modules that will take MIDI directly into them are the Oxi Coral and Neuzeit Warp oscillators
I meant to add here that I opted for the Flame uQMCV and u16CC combo for my Doepfer Rack as they are small and do everything I wanted. Thru, Clock, 4 channels and 16 outputs for CC. They are working great with ARP.
Cheers, I will check it out and add to the list.
The Vermona QMI2 is pretty good too.