This one is a tribute.
X, a famous playback singer, owed a sum of money to some Bengali individual. However, not having the sum with him immediately, he ordered his servant not to let any Bengali gentleman enter his house. As luck would have it, director Hrishikesh Mukherjee, came to visit X, wanting to cast him in the title role of his film A. However, the servant followed his orders to the T, and Mukherjee never even got to meet X! As a result, he caste someone else in the film, which became a huge hit!
On another instance, singer and music composer Y was approached to play a role in the film B. He refused because his father thought it would bring disgrace to his family. Y composed the music for this film, but the role went to X. X and another singer Z practised 21 days before recording a particular song for the film B, which became a runaway hit.
Identify X, Y, Z, A and B.
Hint: the tribute is to X.
I guess most of you latched onto the ‘tribute to X’ hint.
X: Kishore Kumar
Y: R D Burman
Z: Manna De
And the song in question is Ek Chatur Naar.