Barring congenital or surgical alterations of the physical parts needed for speech, if you can breathe optimally you can speak. You just need something to say. And if you have nothing to say then you can say comfortably that you have nothing to say. But if you can speak, especially in public, you do not necessarily know how to breathe.
If you can sing you can speak; that is if you learned to sing from breathing, instead of mouthing the words or "techniques". Focusing on the words and specific body gestures "techniques" gets us locked into patterns that take us away from our natural optimal breathing and the expression of who we are as individuals. Toastmasters comes to mind here. Toastmasterstm is a wonderful way of entry level public speaking and helps instill safety, organization, feedback and understanding of what is needed for functional communication based on organization, time sensitivity balanced with clarity of content. This is extremely valuable to the inexperienced public speaker but there comes a time when the structure becomes limiting and the bird must fly from the nest. Just become more aware of potentially canned robotic body language. The foundation of this new freedom is the freedom of the breath and breathing. National Speakers Association would be a logical nest step. Optimal Breathing private sessions as well.
Opera singers learn techniques but the really great ones seem to express themselves more as individuals and the nuance of their natural personal signature comes through in their voice, facial expressions, body language and the parts they play. Placido Domingo is for me a good example of that. I love it when I watch him he sing and seems to be enjoying himself so. By the way, Pavarotti I am told, worked on his breathing for the first six months of his career, BEFORE he sang.
ACTORS AND ACTRESSES
Actors and actresses are similar. To be able to access the depths of their personal emotional selves to express the thoughts and feelings they are required to play on camera or stage requires opening up the length, breadth and flexibility of their breathing. I call some of my my favorites "breathers". Brando, Pacino, Bogart, Robin Williams, Richard Dreyfus, Eddie Murphy, Elizabeth Taylor, Jane Fonda in that Hooker she played in Walk on the Wild Side, and Paul Newman are but a few. I believe that one reason they are so revered in our culture is that they "breathe" more. Breath really IS life.
Whether you agreed with what they said or not, John F. Kennedy, Jesse Jackson, Martin Luther King, Billy Graham are examples of speakers that also capture(d) and communicate(d) the depth and intensity of passion and conviction. To inspire is also to inspirate; to breathe in. When we become inspired we feel lighter and stronger; more connected to a higher power.
Remember "thinking on your feet". Our breath is the foundation of our creativity. We can have all the answers in our head but if our breathing is frozen we can not access those answers.
Remember a nickname for God? The "creator". Even if we had never heard the word God when we breathe more we get a sense that there is something beyond us or more than us. I believe this is generic to all human beings. I say this because every major spiritual practice or religion has in it some form of singing, chanting, or vocal expression that releases negativity and uplifts one's sense of being bringing the breather closer to their experience and expression of God. And when we speak spiritual words and verbally share spiritual concepts we become more connected with them.
There are many, many, many words but only a few feelings and emotions. What we say interests people but HOW we say it, the breath behind it, is what really inspires them. Words are there to be given shape and deepest meaning from the breath. We are spiritual beings manifesting our spiritual essence in human form through the breath.
Your thoughts are important but they should not dictate your ability to express them. Children for instance, who wish to become leaders and roll models (let THEM decide that) should be developed with a strong internal sense of themselves. Guide them into singing as early as possible. Happy songs. Stand up and cheer songs like God Bless America; Star Spangled Banner; Doe, RE, Me...,Doe a deer, a female Deer, RE a Drop of Golden Sun etc; Amazing Grace (change Wretch to Soul or boy/girl/gal/man/woman) and so on. Let it come out loud and clear. Personal style will develop from that. If you force them into style initially you will stifle their personal expansion and sense of themselves. Michael Jackson may have had this happen to him but he seems to be developing himself the way HE wants to be. God bless him in his transformation.
WHO WE ARE
Adults that never learned to public speak or sing are no different in their lacking of personal sound and expression. Sadly, if they have grown up holding the tensions and fears of abuse and suppression then they may need more time then the children to redevelop their natural ability of self expression.
Most of us have had our breath conditioned out of us. I call this "socialized". When my breath returned after 25 years of searching for it, I knew I could be comfortable in front of thousands of people but I just needed something that I thought was valuable enough to say to them. A reason to take up their time.
When giving a speech or speaking with passion and conviction there is no substitute for knowing your subject.
You MUST know what you exactly want to say or be willing to let it flow from you spontaneously by being familiar with the subject and not be distracted with details. A good example of that would be Ella Fitzgerald. She could sing and when she forgot the words, just make them up and create sounds to match the music. We call it scatting. In public speaking we call that "thinking on your feet".
FERVOR VERSUS CLARITY
Unfortunately many SEEM to know their subject and deliver it passionately and we get lost in the feeling instead of the content. What I call "Multi level marketing madness" and fundamentalist religions come to mind. A sense of peace stemming from the Breathing Exercise #1 or Watching Breath can give us this place of making important decisions without being manipulated by excessive energy. A sense of calm before we take action.
POSTURE AND BODY LANGUAGE
For this to occur and to enjoy the process as it occurs, you must be internally coordinated, balanced, loose, open and tied together. Your voice quality and resonance is a primary indicator of who you are as a person. Your connection with yourself. Your voice, posture and body language are critical. They show that you accept yourself in a calm and clear way or reflect where you do not. It feels good to vibrate when you speak. This good feeling keeps you connected with yourself and that projects on to those you speak with and to.
The foundation of all of this is your breathing. If you can really breathe well you can really speak or sing well.