Singing in the Dark (1957)

Leo, a holocaust survivor who suffers from total amnesia, comes to the U.S. and works as a hotel desk clerk. One night while a comedian who owns a bar in the hotel gives him a drink, he breaks out in song and discovers a great voice. Under a psychiatrist's treatment, and because of a blow to the head by some hoodlums, he realizes his name is David and that he was the son of a great Jewish Cantor, and gradually recovers his memory of losing his parents. He gives up a promising career singing in nightclubs to return to the synagogue.