What kind of song is the stream singing on a sunny day?

From the article "Songs on the Jumping Pier":

On the way to school, there is a shallow stream flowing quietly at the foot of the mountain. In the stream, green stones jump like rows of black keys. On a sunny day, the morning sun reflects the stream. We set foot on the dock, jumped over the stream and walked to school. The stream is singing a happy song.

On rainy days, the river rises. Jump pier and hide in the mud, hide the cat with us. Big brothers and sisters, hand in hand, stood on the invisible pier, forming a long railing. Let's take it _(tāng) across the stream. Laughter and underwater sound blend together, singing a friendly song.

When the water is deeper, the teacher is like a ferry, carrying us again and again, stepping on the underwater pier and crossing the stream step by step. The stream is running and singing a hymn.