Oversinging is "singing too much", or simply overdoing the singing.
Oversinging is not a word found in common dictionaries, but it is a well-known phenomenon. Using an oversimplified example one could say that a singer oversings by "singing too much", as an actor overacts by "acting too much".
There are different opinions on what oversinging implies, though it usually implies one or both of the following:
- Belting to an extreme by singing too loud by pushing one's singing voice "too much" (straining), or singing into a higher or lower range than is comfortable for one's voice (beyond one's useful vocal range).
- Excessive use of runs, whoops, and vocal falsettos melisma.
Oversinging has two meanings. One is a technical understanding, where oversinging is understood as "pushing the voice", and "is when a singer pushes too much breath pressure through the larynx", which is known as overblowing of the vocal folds. The result is over-production of sound.
The other meaning is what is known as "vocal gymnastics". This will imply melisma, and is described by Hollywood vocal coach Roger Burnley as "using too many riffs, runs, and embellishments in their singing".
Singers who try to impress, and show off their vocal abilities, often turn to this kind of oversinging.
When asked about oversinging, professor and voice instructor Melinda Imthurn writes:
Since oversinging is not a technical term, it's hard to define. To one person it might mean pushing the voice beyond healthy singing technique, while to another it might mean embellishing a song too much, sometimes to the point where the melody is no longer recognizable.
Many complain that contestants in shows such as Idol tend to oversing, and blame some of the most prominent American female singers for inspiring them. Some say it has been a rising trend following the many singing contests that started appearing in the early 2000, especially in the United States.
Mariah Carey, Whitney Houston, Christina Aguilera, Kelly Clarkson, Ariana Grande, and Céline Dion are well known for their heavy use of melisma and belting, and they have all been criticized for oversinging. This criticism is mainly focused on too much "vocal gymnastics" which some feel degrades the artistic merits of the song, and not necessarily that they strain their voices too much.
While [Roger] Burnley believes all of those divas to be oversingers in their own right, [Hollywood vocal coach, Chrys] Page argues the opposite. "They don't oversing, but some young hopefuls, trying to sound exactly like those artists, consistently do it because they haven't yet found their own voice and style," she said.
When amateurs on shows like Idol are criticized for oversinging it can be both because they do too much "vocal gymnastics" and that they strain their voice beyond their vocal capability when trying to mimic famous singers with far greater vocal ranges and training.
Professional opera singer Sarah-Jane Dale on Whitney Houston's use of melisma: "You can't do it without proper breath control, and that's the one thing that Whitney Houston had bags of. Let's face it, singers like that do not come along every week."
Straining the singing voice, for instance by using belting without proper coordination, can lead to forcing, which in turn can cause vocal deterioration, known as fatigue of the vocal cords, or vocal fatigue. Straining the voice can lead the development of vocal nodules, a form of scarring on the vocal cords caused by strenuous or abusive voice practices. Professional singers on extended tours with tight schedules run a substantial risk of damaging their voices unless they make sure to rest the vocal cords and get enough sleep and proper diet.
Some famous singers known to have developed vocal nodules are Luciano Pavarotti, Whitney Houston, Freddie Mercury (who refused to have surgery out of fear that it would permanently damage his voice) and Joss Stone. Mariah Carey, although known to have nodules, developed them when she was just a child. 
Singers known to have their vocal nodules surgically treated are Justin Timberlake, Sam Smith, Adele, Björk, Shirley Manson, Keith Urban, John Mayer and Rod Stewart. Julie Andrews is well known for her singing voice being permanently damaged by the surgery. Elton John is notable for having vocal surgery, as it caused his voice to significantly deepen.
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