Credits to the original makers of the song:

Rockstar's whole album is super fantastic but one track that simply class apart is "Kun Faya Kun". In this movie, Ranbir Kapoor has shed his boy next door image and we believe this is his best work done so far. This song is sung by Mohit Chauhan, Javed Ali, and A R Rahman whereas lyrics are penned down by Irshaad Kamil who has also given lyrics in Hindi movie Mausam. Enjoy & play exclusively on T-Series.

Song -Kun Faya Kun
Film - Rockstar
Singer - A.R. Rahman, Javed Ali, Mohit Chauhan
Lyricist - Irshaad Kamil
Music Director - A.R. Rahman
Artist - Ranbir Kapoor, Nargis Fakhri, Shammi Kapoor, Others
Music On - T-Series

The credit for helping me with subtitles goes to Swati Soni. Find her IG on @soni_rambles