How does mouth size affect singing tone?

I was watching an online singing lesson and the lady mentioned this - that a small mouth means less space for sound to "bounce around in".

Would any experienced singers or singing tutors say this is true? How does the size and shape of your mouth affect your tone, volume, etc?

• Well, it does occur to me that the limit as mouthsize-->0 is "humming" :-). That's what I get for being both a musician and a mathematician. – Carl Witthoft Nov 7 '15 at 13:42
• Celine Dion has a small mouth and it works for her! – Cay Apr 18 '17 at 9:00

It's partly to do with resonance in the oral cavity.

A simple analogy might be to imagine bouncing a ball in a small room, and then bouncing the same ball in a large hall. The sound of the ball hitting the floor is reflected around the walls and ceilings - the bigger the space, the more opportunity the sound has to travel, echo and change.

There are other factors involved, and having a small mouth isn't the be all and end all, so I wouldn't let it concern you too much.

Cheers.

• Are there specific things that can be done to mitigate this? I imagine they're probably common to all singers, but might be more important to us small-mouthed singers? – Mr. Boy Nov 4 '15 at 12:23

It's not the size that matters, it's how you use it.

You can enlarge the oral cavity by creating a sensation of starting to yawn. With some practice you can get this feeling without actually carrying through to a complete yawn.

Ultimately, though, I believe the foundation of all beautiful vocal sounds is breath support.

The mouth and other resonance chambers work as an audio filter that can shape the signal from the vocal chords. Put very simply some frequencies are dampened while other are amplified due to resonance. The mouth can be shaped to make certain frequencies stand out. For example to amplify low frequencies you would need a larger volume to make the resonance work - this is due to the physics of sound waves. So the larger mouth space you have, the easier you would find it to make low frequencies stand out.

Some, but it's not a deal-breaker. Heavy-duty opera voices generally come out of quite beefy physiques. But we're not all aiming to fill La Scala without a mic!

It's not the size of the mouth, it's the amount of teeth that show (look at the smile of a singer). Every good singer I have ever seen shows more teeth than those who show less. Look at every good singer's smile. Those with more teeth showing always have a better singing voice.