Clockwork Orange is one of my favorite films ever and that´s for scenes like this one were Kubrick uses objective music making Alex sing "singin´ in the rain" a happy song while he is beating up and raping making our animistic sense feel scared because just a mad men would hit someone while singing a happy song and kick him using the rhythm of he song. When he stops singing and dancing Kubrick uses his typical sound that repeats during all the film that are subjective sounds of bells to make the scene more horrifying than it is.