Measuring the Vocal Athleticism of Broadway Stars

New research using a “vocal Fitbit” quantifies demands of today’s musical theater roles and empowers performers to protect their vocal health.

When Adele was forced to cancel her sold-out shows at Wembley Stadium in 2016, it sparked a fiery debate among vocal health professionals. The then-29-year-old megastar wrote an online letter to her fans explaining that she damaged her vocal folds—an unfortunate relapse from six years earlier when she suffered a vocal fold hemorrhage and underwent risky microsurgery to laser the damaged tissue. 

The backlash was swift: Legions of online commenters blamed Adele’s problems on her powerful style of vocalizing, while some vocal coaches took the opportunity to suggest that demanding performance schedules create lifelong cycles of vocal pathology. Dr. Paul Kwak, a vocal expert and otolaryngologist at NYU Langone, published a defense of Adele to dispel the myth that a vocal cord injury must be the result of bad technique. Likening vocal injury to athletic injury, he says that singing is a “profoundly athletic endeavor.”

Vocal burnout in the performing arts isn’t rare. Sam Smith, Lionel Richie, Bono, Cher, and Michael Bublé are among the many stars who have repaired their vocal cords with surgical intervention. But nowhere are vocal demands greater, perhaps, than on Broadway. Singers there take on challenging roles, belting out show stopping numbers eight or more times a week, and the heavy workload can take a toll.

Now, a new wave of research is offering insight into the vocal demands of contemporary musical theater by employing a dosimeter device that monitors vocal vibrations the way a Fitbit tracks steps. The most recent of these studies, published in the Journal of Voice and led by Ana Flavia Zuim, associate director of vocal performance at NYU Steinhardt and rehearsal pianist for Hamilton on Broadway, drew data from six student performers rehearsing for a production of Frank Wildhorn’s Wonderland, a theatrical spin on Lewis Carroll’s classic novel Alice’s Adventures in Wonderland. 

Students fastened the dosimeter device—equipped with an accelerometer sensor—to their necks to capture vocal fold vibration data while singing in rehearsals. The data helped researchers measure the baseline “vocal dose” required for lead and ensemble roles in the show and compare it with the actual vocal output from student performers. Vocal health professionals typically rely on a singer’s self-assessment of vocal discomfort to assess the likelihood of injury, but more definitive measurements with this kind of “vocal Fitbit” can help establish a threshold of vocal use that is sustainable for singers, as well as illustrate the vocal range required for each specific role in a production. 

For example, the study illustrated how the student-performers used more of their “chest voice,” —meaning the lower range that uses thicker vocal folds and produces belting-like tone qualities through the speak-singing approach typical of contemporary musical theater. Today’s shows are more vocally and stylistically demanding than ever before, which can have an impact on a singer’s vocal anatomy over time, even potentially changing the underlying tissues.

While there are no hard-and-fast rules about how much singing is too much, this kind of data collection is paving the way for future research into the relationship between muscle fatigue and recovery time, and can empower performers to create healthy practices that minimize harm to the voice. 

NYU News spoke with Ana Flavia Zuim about what she’s learned about performance demands young artists face today and the changes she hopes to see in the industry moving forward.

Why is it important to measure what performing in musical theater shows does to singers’ voices?

There's a lot of misunderstanding about belting and Broadway and the vocal impact of singing a demanding role for eight shows a week. Belters use a vocal technique that requires a lot of what is known as chest voice, rather than head voice. 

This study does for the voice what a Fitbit does for the body. A Fitbit might tell you that you burned 400 calories at the gym, while the accelerometer machine I used for the study tells you how many vibrations your voice produces per day and at what intensity—volume—and which pitches—frequencies—were produced with greater frequency throughout the day.

When we talk, treble voices or female voices speak at around 165-250 vibrations per second, depending on the speaker’s age. Male or non-treble voices speak at around 90-120 vibrations per second. When you're singing, they go all the way up—some of the soprano notes can reach 1,000+ vibrations per second. 

But when you're belting, you are at a limited range that is lower than the soprano range—even though you might be a soprano—which means the mid-portion of the vocal folds are colliding more intensely than when singing in head voice. This study allowed us to see what is called the voice range profile, which tells us the intensity for the notes and frequencies used most frequently. The diagrams show blocks of darkness in the main frequency range with a little bit more lightness on the top and bottom notes that were used more sporadically.

This gives us a visual of the “vocal imprint” for some of these roles on Broadway so we can start to obtain an understanding of how “fit” a voice needs to be in order to endure roles of a certain caliber, particularly when a vocalist needs to perform eight shows a week. This is one of the very first studies of this nature, but once these dosimeter devices become more portable and compatible with phones, I expect we’ll see more studies like this one and more data to help us understand the impact of performance on vocal health. 

What exactly is “belting?”

Belting has an urgent, calling sensation where the performers are pretty much yelling the note, and the vocal style conveys a lot of emotion. If you’ve heard Broadway songs like “Astonishing” [from Little Women], or finale songs that are loud, lavishing, and empowering, you’ll know what I’m talking about.

We understand belting as this powerful, guttural sound versus a more operatic sound. While both are demanding, belting is more demanding on the mid membrane of the vocal folds, and there's more muscle involvement than ligament involvement. I previously did a study helping to destigmatize the idea that certain types of vocalisms generate certain types of pathology. Performers are vocal athletes, so singers from any style can be susceptible to injury. 

But what we don't know yet is the threshold of “how much is too much” and exactly how soon the fibers recover, especially with little to no vocal rest in between eight shows a week. We do know that different fibers recover at different speeds—one can recover in a few hours and another can take a day or two or three, depending on the body of the person—but there’s a lot left to discover. 

What is the next phase of this research? 

I’m embarking on a new study with Ingo Titze from the University of Utah, one of the best voice scientists in the country. In this study we ask belters to sing three different phrases in three different vowels around the belting region to create a graph (inertogram) that shows the peaks and valleys of energy in the voice throughout the range. By changing the mouth shape through vowel modification, you can actually turn a valley into a peak and vice versa. The graph will be based on mouth shape and face size, because the unique anatomical configurations of your face and throat give you a vocal print that is unique to you. 

That's why your voice might sound like that of your mother and your siblings. But it's slightly different, because even though you may have some of the same features in terms of face and neck shape and size, there's enough nuance in you to affect the frequency of your voice. This graph is going to help us understand how different individuals can change their mouth shape while vocalizing (such as using an “ahh” vs. an “ohh”) to produce a specific result in terms of vocal quality and impact. Your unique anatomy, as well as the ways you shape your mouth, act as a filter to the pitches you produce. By understanding how a person’s anatomy affects the way they vocalize, we can help vocalists to make changes in their mouth shape to produce a better boost to a particular note with less impact on their voice. 

How have the vocal demands for performers shifted as musical theater scores evolved? 

In the 1910s, the dominant form of musical theater was operetta, which was a lighter form of opera. As the decades went on, we witnessed the creation of burlesque, cabaret, and vaudeville which included more spoken word and lower vocal ranges. Eventually, we developed musicals with story throughlines. Oklahomagave birth to the concept of a book musical—the plot of the story was intertwined with how the song was written. Ideas about the prosody of language and understanding how to communicate story through melody became more ingrained.

With the birth of the radio era, Broadway started influencing the radio. Rock and Elvis Presley became dominant and Broadway began adapting with the creation of Hair and Jesus Chris Superstar, among others. This led to jukebox musicals taking pre-existing pop songs from the radio and constructing a plot. Examples include Priscilla, Queen of the Desert, which used disco songs, ABBA musicals with Mamma Mia, and Jersey Boys, inspired by the Four Seasons. With rock, there's a lot more of this calling, belting vocal style.

Hamilton was another huge transition, because now we have rap involved in musicals and the rap is telling the story. There’s no dialogue outside of musical content. It’s a difficult score—the Lafayette rap in “Guns and Ships” has more than six words per second. All these styles are intertwined on the Broadway stage, which creates artistic innovation but also requires different stamina from singers.

Vocal demands have changed drastically across genres and styles, requiring tremendous vocal versatility from Broadway performers. In academia, there was a longstanding tradition of teaching singing through opera or the bel canto traditions. But with this evolution of vocal styles we now are faced with the need to prepare students for the current vocal performance market. We must also help them understand how they can protect their vocal health and prevent injuries in the process.