How can we best encourage clear speech in the child? Just as in walking, a child learns by seeing us do it well, so in speaking, a child needs to hear us speak well, rather than hear us speak like him. It is of great value to speak clearly and naturally to the child, rather than using baby talk and speaking in a baby-like manner. Not only does is show respect towards him, but his language development starts long before he speaks, and exposure to good language gives him a worthy model to imitate.              

Singing and nursery rhymes are a wonderful thing for babies and young children. They expose them to rich language that they don't encounter as much in everyday speaking, as well as awakening their natural sense for music and rhythm.

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From Research Institute for Waldorf Education Here is the article:

Non-Verbal Education- A Necessity in Development Stages - Michaela Glockler

Boy and bird by Rubens