The volume was diminished by pushing the button.

The school disposed its strict school rules.

Only this sample is disproportionate, compared with the others.
klingt das natürlich?

Normally, when discussing loud volume, the main verbs that get used are "lower", "decrease", and the extreme "mute". There are others but these are the mainstays, I think.

In the second example, I would use "rescind" instead of "dispose" for that context.

Finally, using the word "disproportionate" without concrete examples being mentioned is tough to remember or follow in my opinion.

My examples:
1. My boss' faculties were diminished by Alzheimer's disease.

2. The school disposed of the rotten pork in the cafeteria.

3. The American waistline is disproportionately larger than the Japanese waistline.

These are extreme examples but I find it easier to remember them mnemonically that way.