Mithrandir said:
-"Lord Vader, can you hear me?"
-"Yes master"
-"To cheat death is a power (...)"
- (Vader interrupts palpatine) "She no longer means anything to me master... now (...)"
Good idea but voices are not in the same tone, there is a too obvious difference between : "can you hear me" and "to cheat death"
The compatibility is an essential point to make a good audio cut.
It's not easy to mix voices from different scenes.