Agree it is unique however, nowadays, nobody trains themselves to regulate the tempo and modulate their voices. Deep voices have become a rarity in India.
Not only acting but voice also makes a film great.For that matter Shatrugnsinha had a good voice and in Telugu movies late Rao Gopal Rao and Srihari had a impressive and commanding voice.So voice and speech are more important to a movie.Similarly Rajani Kant also has a spectacular voice.
so, what is so great about that, and that also a voice,raj kumar also had a voice,only by the voice a person can be recognized.if in these days he will do a good film, and that is what it matters. after 1981 not a single movie starring him is watchable, this is the pririoty he should accept.