To get the musical key of a track you can use the free software KeyFinder, which can be called from Yate.

1) Download KeyFinder from here: http://www.ibrahimshaath.co.uk/keyfinder/ and install
2) Download the script: https://gist.github.com/Powder/5712869/raw/ce2e7d731288ac32af816e9a6009e4cbed7ff5e4/getkey.sh
3) make the script executable using chmod +x getkey.sh
4) To call it from Yate create a new Action and add the following functions:
Run external script and pass File as Parameter, save results to Variable1
then you can copy the value from Variable1 in Initial Key using the copy function