Transcript for What Happened to Mariah Carey's Voice at Rockefeller Tree Lighting?
And now to the live televised flub that is creating an online feeding frenzy tonight around one of America's leading ladies of music, Mariah Carey. ? All that you could ever know ? Reporter: It start ed out well enough. Mariah Carey performing live at the Rockefeller tree lighting ceremony on NBC. Then she starts missing her signature high notes. Snsz F ? for Christmas ? Reporter: The cracks are even more apparent in this video, where the vocal track is isolated. ? For Christmas is ? Reporter: The social media response was fast and furious. Detractors saying, please give it up. And it was painful to watch. Suggesting her ex-husband nick cannon must have got her voice in the divorce settlement. Her fans pushed back, though, saying people should cut her some slack and she's a living legend. But how could it be that this legend with a five okay taif vocal range, famous for hitting the high notes like this one in "Vision of love." ? Reporter: Could suddenly sound so off? She's sick. That was my very first reaction. ? Reporter: Vocal coach to dozens of Broadway stars, Matt Farnsworth knows first hand what can happen when a huge star like Mariah performs life. When someone doesn't feel well or someone is performing in front of millions of people on live television, it's very stressful. And the first thing that sometimes happens is, you stop breathing and the voice is a wind instrument. Reporter: To be fair, it's been 20 years since she first recorded the best-receiving Christmas single of all time and so damage to her voice may have added up since the days when she could easily get into the upper register. ? ? oh baby ? How did that go? It was good. I didn't have to sing, so. Reporter: As seen in the show "Mariah uncut" on E, she's had to visit a throat doctor before. We see that vow vocal chords are swollen. I have to tell you, you're going to have to cut down on the promotional push that you're doing. ? Santa Claus can make me happy ? Reporter: Vocal wear and tear is a scary proposition for a diva whose fame and fortune rely on an aging body. That is something John Mayer, famous for "Your body is a wonder land" knows all too well. ? Your body is a wonder land ? Reporter: In 2011, he developed a granuloma on his vocal chords. Emotionally super fragile in this period of time. Because? Because I don't have a job. Reporter: The job followed Mayer as he got a scope done. Tongue out for me, please. Reporter: It's a procedure many professional singers, like enkenje here are familiar with. She's currently starring in "Motown" the musical on Broadway and she's been struggling with throat issues. What we see here first is what looks like an upper respiratory infection. Understand that this is not terrible and the most important thing for me is your reflux isn't so bad. All right. Reporter: As somebody who is starring in a Broadway show, when you feel like your voice may be about to go, how stressful is that? Very stressful. Absolutely. Because you're in the middle of a show. There's 1,500 people out there. If you are starting to feel it, then you have to sort of try and compensate differently in how you sing the rest of the show. In order to get through it. Reporter: She will recover with some extra rest. In fact, Dr. Kaufman stresses that rest and eating healthy are the keeps to a healthy voice. Is it simply the case that as we get older, our vocal chords wear out? If you sing hard, you tend to get some scarring. Reporter: And Mariah sings hard. Chef doeshe does. Reporter: If she had a growth on her vocal chords, all is not lost. It's fixable. It doesn't mean they're cooked. Reporter: Her days of hitting the high notes are not necessarily over. Yes. Reporter: Good news for everybody. Good news. ? I love this girl ? Reporter: Surgery was a last resort for Keith urban. And Paul Stanley of kiss, who both risked putting their most precious asset under the knife. British singer Adele did it too in 2011. ? Someone like you ? Reporter: The singer is known for her raspy voice. And vocal coach Matt Farnsworth says that tone is noticeably different since her surgery. She had to restrain her voice and she has a slightly different sound to her voice but she's singing healthier. Reporter: That said, Adele expressed relief about her results in an appearance on "60 minutes." I can't remember a time where it felt so smooth to sing and not be paranoid on stage. ? The hills are alive with the sound of music ? Reporter: Though surgery worked for Adele, it ended Julie Andrews' career in 1997. The legend would rarely sing in public again after she says a botched surgery to remove nodules limited her range and her ability to hold notes. A routine procedure that I was told would not be threatening to my vocal chords. Reporter: As for Mariah, whatever caused last night's blunder, this diva has plenty of experience in bouncing back. Anyone remember that film classic "Glitter?" She survived that flop. And maybe next year she'll pull in some help from her holiday appearance from a younger friend like Justin Bieber.
This transcript has been automatically generated and may not be 100% accurate.