This app was mentioned in 5 comments, with an average of 2.40 upvotes
The way the app works (in this case) seems to be that the original artist (the woman here) pre-records their part, and then the user of the app can add their part of the duet to it, after which both appear combined in the final video: https://play.google.com/store/apps/details?id=com.smule.singandroid&hl=en
Videodaki uygulamayı bulamadım ama bunu buldum