This manual describes how to install our OrganDonor midi interface in Oberheim 4 voice and 8 voice synthesizers.
You can purchase the kit here: Shop: Organ Donor

Picture derivative work:
Robert Brook, CC BY 2.0 <https://creativecommons.org/licenses/by/2.0>, via Wikimedia Commons
The installation guide can be downloaded as PDF here
The config file for OrganDonor is here