Who came up with the idea of sound music?

The concept of "sound music" isn't a commonly used term in music theory or history. It's possible you're thinking of a specific genre or style of music that uses the word "sound" in its name, but it's not clear what you're referring to.

Could you please provide more context or clarify what you mean by "sound music"?

For example:

* Are you thinking of a particular group or composer who used the term "sound music"?

* Are you referring to a specific genre like "soundtrack music" or "sound design"?

* Do you have any examples of music that you consider "sound music"?

With more information, I can help you identify the origin of the idea.