Vibrato in Legit Musical Theatre Singing
Updated: Feb 23, 2022
Vibrato is a feature of legit singing, but what exactly is it and how do we use it in this genre?
What exactly is vibrato?
Vibrato is a musical effect consisting of a regular, pulsating change of pitch. When describing vibrato we talk about how much pitch variation there is (extent of vibrato) and the speed with which the pitch is varied (rate of vibrato).
I personally find it easier to understand vibrato by seeing a visual representation of the sound.
Example 1: An A4 sung by a female soprano with vibrato
In the above image the singer is singing an A4. You can see the note marked on the keyboard and you can see an orange line that shows the fundamental pitch. You can also see a blue wiggly line that shows the actual vibrato pitch. The vibrato pitch moves up and down, yet the fundamental note we hear is still perceived as an A4. Extent is the average movement above and below the the note and it is measured in cents (a semitone is 100 cents). In this example the movement is approximately 50 cents (a quarter tone) above and below the note, giving a total extent of 100 cents. If the extent is too large then the singer will no longer sound in tune. But in this case of an extent of 100 cents the note is clearly perceived as the A4.
If the extent of the vibrato is very small, then you have a straight tone, which is totally fine for contemporary singing and some styles of choral singing, but not what you want for legit musical theatre.
Example 2: A soprano singing a straight tone on an A4
You can see in the above image that the pitch still moves, but that it moves a lot less than when the note is sung with vibrato.
The second element is the number of times per second (Hz) that the voice moves above and below the pitch, the rate of vibrato. Miller, who writes about classical singing, states that around 6 or 7 Hz would be considered a normal vibrato rate, and more recent research shows good vibrato rates are between 5.6 and 6.9 Hz. In Example 1 the singer's vibrato rate is about 6 Hz. If our production of these undulations is too slow, probably around 4 Hz, the voice will sound wobbly and will be described as a wobble and not vibrato. If it's too fast it would be a tremolo and not a vibrato.
What is good vibrato?
Although we can measure the extent and rate of vibrato, there is no doubt that teachers and vocal coaches have different opinions on what sounds good. Musical tastes are also changing, so what was once considered a great vibrato can now sound too wide or over the top to modern ears. In addition to extent and rate, we must consider the timbre and changes in volume (the amplitude) through the vibrato, which will also impact what we are hearing and how we feel about the vibrato. And there is the question as to whether the vibrato you are using is appropriate to the piece you are performing.
In legit musical theatre we do expect vibrato to be in the singing. Kelli O'Hara is an amazing legit musical theatre performer so I decided to take a look at her vibrato in an unaccompanied version of To Build A Home, from Bridges of Madison County. I realise that the piece is a bit of a blend between legit and more contemporary musical theatre, but I picked it because you can clearly hear her sing without the sound being obscured by instruments.
In legit singing it is common for there to be vibrato through the whole sung line. It is noticeable that Kelli O'Hara is not doing that in this piece. She is using her vibrato for artistic expression where it varies from phrase to phrase and sometimes within the same word. For example on the words "nervous bride" she begins using a straight tone on the first part and then brings in her vibrato on "bride". On the word "bride" we have a mean vibrato rate of 6.6 Hz and an extent of 71 cents, which are within the expected ranges for legit singing.
If we look at the word "harbour" we can see that her vibrato rate has increased a little to 7.0 Hz and that the extent is also wider at 105 cents. This makes the word sound more dramatic than previous words and it is being used to express her emotion at this time. If we analyze the entire piece, the average (mean) rate and extent are certainly within the range of vibrato we expect for legit singing, but throughout the piece the it changes depending on how she feels and how she chooses to use it.
I find Kelli O'Hara's vibrato to be very pleasant, but there are other brilliant musical theatre performers who have a vibrato that I do not enjoy as much. Michael Ball, for example, has a wider vibrato with an extent that is larger than 150 cents, and I am not keen on that. But then Audra McDonald has a wider vibrato, which in one example gets to over 200 cents, yet I love how she is singing the song with a mix of contemporary and legit expression, which makes it sound incredibly emotional and true.
What is considered to be bad vibrato?
Firstly you can be told that your vibrato is bad, when really it's just the wrong type for the song you are singing and there is nothing functionally wrong with it at all. For musical theatre we need to learn to sing with and without vibrato, depending on the expected style. We also need to learn how to remove it and then add it on to the end of note.
There are, however, some types of vibrato that we want to avoid:
Three terms that are often used to discuss less than desirable vibrati are wobble, bleat, and flutter. Wobble is usually a vibrato with a wider extent and a slower than desirable vibrato rate (2–4 Hz), while bleat or flutter is a vibrato that has a narrower extent and a faster than desired rate (up to 8 Hz). – John Nix, Journal of Singing, March/April 2014
I have also heard the terms "natural" and "unnatural" used to describe vibrato, where "natural" is good, and "unnatural" is bad. Natural vibrato is the sound that occurs when the voice is free and relaxed. You aren't consciously trying to produce it. Unnatural vibrato is created by the singer by moving something like their jaw, head, or chin or by playing with air flow. You can also produce a vibrato by singing whilst standing on one leg and shaking the other. This can be a good exercise to let you hear the sound and feel it, but probably is not how you want to perform.
I personally don't think that producing vibrato by doing something like moving your jaw is bad; it's a stylistic thing that works in genres like gospel. Pop singers are often doing things to stylistically use vibrato and they can be deliberately creating those sounds. That being said, you don't want to be moving your chin, jaw, or head, to be producing vibrato for legit musical theatre. I have seen singers that do this and it takes away from the meaning of the words as their head movements don't match what they are singing. It also won't allow you to produce vibrato through an entire lyrical line, as it's used to do things like add vibrato onto the end of a sustained note that has mostly been sung with a straight tone.
What if I can't produce vibrato?
I believe that you can learn to produce vibrato. For some people it just happens when they are singing with good vocal technique, but others learn it through doing exercises. I would recommend looking at the Youtube videos by Justin Stoney as he has a great series on producing vibrato starting with Ep. 30 "Vibrato 1- Pitch Changes" - Voice Lessons To The World.
Vibrato is just one element of legit singing, and you can read more about legit singing in my other post: Legit Singing in Musical Theatre.