I find having music playing in the background incredibly immersive.
I found these on Youtube (caveat - I haven't played through them in their entirety)
https://youtu.be/flMGQmZE84A?list=PLB7bt4NL6c_1tuD-jsFni0cNrQZJFvd6G
https://youtu.be/KxcP7TRY178?list=PLB7bt4NL6c_1tuD-jsFni0cNrQZJFvd6G
https://youtu.be/ST353mDWL3Q
https://youtu.be/BJepYzH1VUY
https://youtu.be/lDnva_3fcTc