This is the latest description of the firmware, voice packs and CPS of the Open GD77 project as of 6/16/20. Here is a link to the most up to date package available. Be sure you download the latest package and re listen to the MP3 files or read the PDF files that comes with the software in the newest package. 

http://www.spencerweb.net/Downloads/OpenGD77/opengd77.html