Season 1 | Episode 9
What do a trembling hand, an emotional speech, and a soaring operatic phrase have in common? Vibrato.
Welcome to The Voice Science Podcast, where we dive into the science behind all things singing and teaching. Here, you’ll learn how the voice works and discover practical tips to train it more efficiently. I’m Drew and I’ll be your guide for this exciting episode about vibrato.
To the average music listener, the presence of vibrato in the voice or played on an instrument communicates warmth, richness, and emotional depth. The sound appears to flutter, tremble, or shimmer. According to John Nix, university voice professor and voice science researcher, vibrato is “the periodic oscillation or variation of the fundamental frequency (pitch) and its harmonics as well as the oscillation of amplitude (volume).”
If you are thinking “That’s great; but, how does it work?”. We don’t know for sure.
The definitive cause of vibrato in the voice remains a mystery to voice scientists. There are numerous theories floating around. Most of them fix their starting point with neuromuscular behaviors common in the human body, known as physiological tremors. These involuntary, rhythmic movements, present in all healthy individuals, exhibit as fine, rapid oscillations, often located in the hands, fingers, head, and the voice. The causes of these physiological tremors is normal muscle use, stress or anxiety, caffeine or nicotine use, and certain medications, just to name a few.
Simply put, these kinds of physiological tremors are part of being human. Have you ever witnessed someone shaking in anger or fear? Or acting jittery in a state of worry or nervousness? Are you a person who is prone to unconscious teeth grinding? What about someone’s voice trembling when experiencing intense sorrow or joy? Or the impassioned public speaker’s voice as they reach the climax of their address? Clearly, the human voice, can become tremulous, due to an elevation in both rate and extent.
As it relates to the singing voice, the renowned voice scientist Ingo Titze believes that “a reflex mechanism with a long latency (i.e., delay) is implicated as a possible cause for vocal vibrato.” This theory, also known as the reflex resonance model of vocal vibrato, suggests that vibrato occurs due to the behavior of the muscles responsible for the length and tension of the true vocal folds, namely the cricothyroid and thyroarytenoid muscles. The oscillating one hears is the result of a kind of muscular call-and-response where one muscle contracts while the other responds by relaxing, creating a feedback loop, in which each muscle seeks to correct the action of the other muscle.
To illustrate this, recall if you have ever overheard someone tuning a stringed instrument. One technique you will notice is intentional pulling of the pitch of the string above and back to center, and/or below and back to center of pitch. In a similar way, the cricothyroid and thyroarytenoid muscles are engaged in a cyclical game of correcting the pitch back to the center.
Professor Nix suggests that a singer learns how to take the naturally-occurring feedback loop (the reflex resonance model of vocal vibrato) and entrain with it. If you are not familiar with this word from the world of biology, to entrain is defined as the ability to fall gradually into synchrony with a rhythm or something that varies rhythmically. With practice, singers become consciously able to regulate and monitor their vibrato.
Monitoring vibrato requires monitoring two separate parts of vibrato, the rate and extent. Vibrato rate, is the speed of the oscillations per second measured in Hertz; and its extent, the distance above and below the central pitch measured in cents. Not cents as in pennies, but cents that measure the frequency fluctuation. One hundred cents is equal to a half step, the distance between two neighboring keys on a piano, with fifty cents equivalent to quarter step. Culturally in the West, a good vibrato is defined as having a rate of 5-7 Hz with an extent of plus or minus fifty cents. If the vibrato is slower and wider, it is considered a wobble. If faster and narrower, it’s a bleat or flutter.
Let’s turn our attention to unlocking vibrato. It has long been the consensus in the voice teaching universe that vibrato will reveal itself when a singer’s vocal production is well-coordinated, therefore well-balanced, meaning not over-produced, particularly at the true vocal fold level where the cricothyroid and arytenoid muscles reside. As the reflex resonance model of vocal vibrato stands as the most viable explanation for the presence of vibrato, it is essential that the muscles responsible for creating the feedback loop move without any undue suppression of their activity.
As simplistic as this illustration is, it will serve to make the point. Hold out one hand, palm down, and rotate it side to side until it starts to tremble. Now, place your tremoring hand palm down on a flat surface. Doing so will stop or substantially reduce the oscillating motion. If it does not, place your other hand on top of the hand on the surface. At this point, all motion should be suppressed. Likewise, if the function of the true vocal folds is being constrained, the presence of vibrato will likely remain hidden.
So, the best approach to finding and using vibrato is to build a solid vocal technique under the guidance of a knowledgeable voice trainer. If private or group coaching is out of reach there is no shortage of free advice available on the internet courtesy of a plethora of vocal coaches selling their services and merchandise. Unfortunately, not all of the advice is scientifically sound. By far the least beneficial advice we have found is: sustain a pitch while shaking your hands in front of you. As silly as this sounds, it may have the benefit of loosening a body filled with tension, but it should not be confused as a serious suggestion for allowing vibrato to emerge. Another piece of advice is: just do an imitation of a opera singer with a big vibrato. Again, other than a bit of silliness, we question how this act of imitation is guiding a singer towards a well-balanced sound that will allow the vibrato to reveal itself. If you have questions about the advice you are finding online feel free to reach out to us at VoSci.
Some vocal coaches do recommend abdominal-respiratory pulsating as a gateway. This approach requires rapid abdominal muscle contractions causing subglottic air pressure to change the fundamental pitch. The main problem with this approach is it remains a substitute for the reflex resonance model discussed earlier.
Returning to the premise that the best approach is securing a well-balanced vocal production, some of the better internet vocal coaches suggest vocal agility exercises as a pathway to unearthing the vibrato already residing but hidden. Examples of these types of flexibility exercises contain elements such as: pitch bending; half-step and whole-step trills; staccato laughing “he-he-he”; running passages of notes followed by a sustained pitch—the place where the vibrato can begin to appear. As required for success, these exercises require a thinner true vocal fold mass which yields a light and softer quality of sound—perfect for any singer who habitually sings heavy and loud, with the result being frustration because vibrato is difficult if not impossible to find. These types of exercises can be a key to finding the well-balanced vocal production you’ve been seeking all along.
To recap, vibrato is a naturally-occurring phenomenon as a result of the reflex resonance model of vocal vibrato. It is not just for some; it is available to all singers.
If vibrato is missing in a singer’s voice, it is probable that the current approach to vocal production is suppressing the ability for the vibrato to emerge.
The goal of any singer is to develop a well-balanced vocal production which will allow them to discover the vibrato in their voice and learn to entrain with it.
Thanks for listening to The Voice Science Podcast. If you found this episode helpful, consider sharing it with a fellow singer or teacher. And if you’re curious to learn more about vibrato or any other aspect of vocal technique, check out our resources at voicescience.org. You can also connect with us directly—we’re always happy to help you make sense of the science behind your sound.
Until next time, keep exploring, keep practicing, and keep singing.
Josh Manuel
Founder/Editor
Timothy Wilds
Writer