"Deeply pained to learn of the passing away of Mehdi Hassan in Pakistan... a vocalist of immense fame and unique sonorous voice," Amitabh tweeted.
"Mehdi Hassan, an entire era of soulful ghazal singing gone... now left with beautiful memories and personal meetings with him," he added.
The legendary Pakistani ghazal singer, born in India, passed away at a Karachi hospital Wednesday after a prolonged illness. He was 84. He will be laid to rest Friday.
Recalling his meeting with Hassan, Amitabh wrote: "Mehdi Hassan once told me, he came from humble beginnings, and used to train and sing to the tone of the tractor sound in the fields."
J. Jayalalithaa passes away: Her life in pictures
Photos: Shah Rukh Khan, Deepika Padukone, Alia Bhatt at an awards show
Photos: Big B, Iulia Vantur at Himesh Reshammiya's album launch
Photos: Aamir Khan with 'Dangal' actresses at fashion show
Spotted: Twinkle Khanna, Shriya Saran at an event in Mumbai