Midi is a more reliable method but there aren't many polyphonic voltage to midi converters in Eurorack. As of now there is one module that has been designed specifically to integrate the ND in a modular system.
Ladik M-218 http://ladik.ladik.eu/?page_id=1972
I'm not connected to Ladik in any way but I have has some indirect input into the design of this module as I know the ND user who has been working with Ladik to make this module happen. It will work directly with the NDs default midi setup out of the box but alternative note and channel assignations can be applied. The 6 inputs interpret the incoming voltage as midi note velocity so its easy to patch up accents and other expressive variations. And the output on midi DIN means there is a direct, one cable connection to the ND.
Just needs a red faceplate really...
