A song is born - in story and pictures; What Sadie Sang, story and pictures by Eve Rice. New Edition. New York: Greenwillow Books. Pages unnumbered. $9.50. Ages 2-5.

This simple, precious book - originally published in 1976 - will speak to all parents who are experiencing the first ''sounds'' of communication with their children. It will speak to little children because they understand so well the special intimacy that flows between themselves and their parents as a result of those first toddler babblings.

Sadie, teddy bear in hand, is taken for a long neighborhood walk in her stroller. The stroller's sticky wheels go click, click, click - ''Gee!'' says Sadie (with a hard ''g'' and a long ''e''), and her song is born. Sadie sings to a ''tree on the corner,'' a ''red, red fire hydrant,'' spring tulip, scratching dog, and other selected things both animate and inanimate. A neighbor thinks she is crying, the grocer thinks it's a toothache. But her Mama understands that it's Sadie's joyous affirmation of those newly discovered, commonplace things. Sadie needs no response. Her song freely bestows a kind of blessing on the facts of her environment. The song ends as she falls asleep in her bed - looked on appreciatively by a smiling stuffed penguin.

Eve Rice's illustrations couldn't serve her own text better. Each page pictures things that toddlers seem to first respond to and ''name'' - a teddy bear, cat, bird, boat, ball and bat. Young listeners will love identifying these familiar objects.