Farhan along with Big B recorded the track about unusual friendships here last week.
It is the first time that the Bollywood stars, known for musical prowess as well, have given their voice for a song together. The track has been composed by Rochak Kohli and penned by Gurpreet Saini and Deepak Ramola.
"Performing a song for such a film ('Wazir'), with such wonderful people... which has been composed beautifully by Rochak has been fun and it feels wonderful," Farhan said in a statement.
In some of the photographs that were shared by Amitabh last week, the duo can be seen having fun while recording the track. Farhan is also seen holding a guitar while singing.
"Atrangi yaari", which forms the crux of the Bejoy Nambiar directorial, depicts the unusual friendship between the characters played by Amitabh and Farhan.
Explaining the origin of the song, Vidhu Vinod Chopra, who has produced the film, shared that "I was searching for a song since the last six months. I heard around 100 to 200 songs and I had almost given up before I came across this song."
Big B flew down from Kolkata to record the song. He said: "I was shooting in Kolkata at night, he (Chopra) called me and said this is the song, you have to sing it, we have to shoot this and this has to happen very soon. So, here I am."
'Wazir' will present Farhan as an ATS officer, while Big B will be seen essaying the role of a physically disabled man with a sharp brain. Aditi Rao Hydari will be seen as Farhan's love interest.
The film will release on January 8 next year.