Big B spoke at the launch of "Mohammed Rafi My Abba - A Memoir", a book written by the singer's daughter-in-law Yasmin Rafi, here Sunday.
"When we look at the great amount of work that he has left behind, we must be astonished now because Rafi saab rendered the songs at a time when the support of the technology was not there," said Amitabh.
"Today's music directors and technicians and singers, with all due respect, have the benefit of technology. You sing slightly 'besura' and there is a lovely machine that puts you in tune," added the 70-year-old, who has himself crooned some of his own songs.
The actor says he has great admiration for Rafi, "because he lived through a time and performed through a time when he was not supported by the modern technology that we have today".
Amitabh also spoke of Rafi's versatility, and recalled how he used to mould his voice according to the actor he sang for.
"Before singing a song for a particular actor, he used to ask, 'Which actor am I singing this for?' Then he would alter his voice or do something. Whether he was singing for Shammiji (Kapoor), whether he was singing for Dilip saab (Kumar), you felt that yes, this is Dilip Kumar singing or Shammi Kapoor singing. This is a quality which is very rare among the playback singers," he said.
Rafi is known for songs like "Chaudhvin ka chand", "Teri aankhon ke siva" and "Tum jo mil gaye ho".