https://youtu.be/FDoZUAJ7ZhI
I found this.. it has all the instrumentals used in drama.. number 6 is the one that TEGIN song which plays for Ashile Sun.
There's a documentary about how the music for the drama was created too on You Tube. The link below is a shorter version of it.
https://www.youtube.com/watch?v=Cr1XZIVXTho&t=269s