There have been many varied definitions of music, dependent on
writer's idea of, or appreciation for, music. One man's music is another man's noise. And he defines accordingly. One says Nevin is music and Bach is noise. One declares Mozart to be noise and Stravinsky, music. Another reverses
definition. Even
dictionary tells us that "music is
art of combining tones to please
ear."
Whose ear -- yours or mine?
A French writer, Jules Combarieu, is more general, and declares it to be "the art of thought in tone." In other words, it is an art, not a natural phenomenon; it deals with tones, and it presupposes thought; that is, educated mental action and discrimination. "Thought, using tone as its medium, creating an art work."
And still, this leaves open to discussion, "What is an art work?" We journey back to
starting point, you saying Mozart created art works, and Schonberg didn't; while I may pin my faith to Cadman and Herbert.
One might reduce
definition a little, and make it more generally satisfactory, by saying music is "thought expressed in tone." This would exclude noises -- casual, unbrained combinations of tones -- and require definite mental application, presupposing a knowledge of
essentials of musical construction.
While this definition may be satisfactory to you and to me, there are those whose idea of music is so different from ours, that only a definition to fit their own particular style would suit them.