WHY IS MY VOICE SHAKY WHEN SINGING AND WHY DON’T I GET A VIBRATO WHEN SINGING LOUDLY?
Both of these extremes have to do with the ability to pace the flow of the breath in coordination of the vocal cords as they come together to vibrate a tone.
— When the vocal cords are too lax or the breath support insufficient, the voice will shake.
— If the vocal cords are pressed together too firmly and if the flow of air is excessive, they will not be able to oscillate freely enough to produce vibrato.
— Volume comes from RESONANCE, not from force. Singing softly is not the result of collapsing or in any way relaxing – it takes even more support than loud singing.
Try to take some lessons with a good singing teacher or voice coach. He or she will have exercises to help as well as suggestions for how to do them most effectively.
You can also find useful information and tips in the answers under the categories of Breath, Phonation and Resonance.