If you’re cooking a recipe. You need just the right amount of ingredients. Too much of one thing can upset the balance of the whole.
Very often, when we our creating art, the temptation is to fall into the trap of adding layers and layers without letting the work we do breathe. Or on the contrary, we do too little and then don’t consider the levels of detail we can add to bring a level of sophistication to our work.
Depending on the intent, finding the sweet spot matters. Adding harmony shouldn’t be just done because it can be done. It should be done because it feels right to do so.