Music Machine (1991)

While flying a kite on a hill, two children named Stevie and Nancy are swept away aloft by their kite in sci-fi fashion to a fantasy, wonderland-type world called Agapeland. It is a lush green place near a river, containing over-sized mushrooms, living plants, and friendly woodland animals. Shortly after their arrival in the pleasant Agapeland, Stevie and Nancy discover the Marvelous Music Machine, which Stevie explains is a "quanamatic digilator." Stevie tries to make it work, but only succeeds in causing it to produce a loud noise, which shoves him back into the Music Machine's caretaker (possibly creator), The Conductor.

Unfortunately the movie Music Machine is not yet available on HBO Max.