Explain ????

I’m watching season 7 episode 18 , Song Beneath the Song. (PLEASE SAVE YOUR OPINIONS ABOUT THE EPISODE).

All I want to know, is HOW, are they able to use two Calliopes? Stunt double? Twin? Look a like? Green Screen? Whatever you call it.. How are they doing this???

I’m watching season 7 episode 18 , Song Beneath the Song. (PLEASE SAVE YOUR OPINIONS ABOUT THE EPISODE).

All I want to know, is HOW, are they able to use two Calliopes? Stunt double? Twin? Look a like? Green Screen? Whatever you call it.. How are they doing this???