Years after the peak of her success, Whitney Houston's unparalleled voice was "gone" and it took years of coaching sessions to get even part of it back, her one-time vocal coach revealed to "20/20."
"It appeared to be so damaged that when I first began working with her, I was not sure what I could do," Gary Catona said.
See the full story on "One Moment in Time: The Life of Whitney Houston," a two-hour "20/20" special, TONIGHT at 9 p.m. ET.
In the 1980s and 1990s, such ballads as "I Will...Full Story