Well, “let’s start at the very beginning...”
Singing is something like talking, but very special. The human voice is the one musical instrument we carry with us at all times. It is unique. It is warm. It can convey thoughts and feelings better than any other musical instrument. It is a gift from God. We develop our ability to speak from infancy. Singing should be encouraged from infancy as well. Babies must be allowed to exercise and experiment with their voices. How very sad it is when parents try to silence their babies when they are just vocalizing.
Singing is a very social art. Join in and show the baby how singing is done. Show them how enjoyable it can be. Show them how to make modulated pitches. Play silly vocal games with the baby. Interact using facial expressions and gestures and touching and clapping and bouncing. Make crazy noises. Imitate their noises. Sing little songs and even nonsense syllables and rhymes. Practice rhythm. Over exaggerate repeated consonants such as buh, buh, buh, buh or guh guh guh guh. Sing sirens sliding from high to low. Purse your lips together and buzz like a motorboat on pitches high to low. All of this will establish an environment for vocal experiment, but it will also help the babies develop their ears to match pitch and become acquainted with musicality.
Now, this is a cautionary tale. We are all humans and as such, we develop our own ideas of beauty. What I may epitomize as the most beautiful voice or style of music, someone else may dismiss as too highbrow or too earthy or too commercial. Fortunately for me, my upbringing exposed me to a wide range of musical styles and voice qualities. I happen to think that if we all sounded alike, the world would be a dull place indeed. However, I think that in singing, we can all strive for better intonation, blend, balance, breathing, and attention to pitch. There is nothing quite as heavenly as a choir singing IN TUNE.