Learn English – the word for “the way a word sounds to your ear”

I don't think the English usage of "scene" carries the negative connotation. If I were joining a university, for example, I might ask about the "downtown scene", "bar scene", "sports scene", or "student life scene" and I wouldn't be inferring anything negative.

Actually, it's pretty unusual for someone in English to use the term "scene" negatively, and people generally tend to use more inflammatory words such as "agenda." You will find this most often in politics. For example, in the United States you will find that far-right leaning people will often talk about the "gay agenda" or the "liberal agenda", inferring that there is a sort of subversive current.

If you are talking about music, I suggest instrumental. Compositions with non-lexical inclusions (such as "la la la") or occasional words are considered instrumental too, according to Wikipedia.

If you want to include non-musical sound as well, such as the machine gun recording that you mention, then I suggest non-lexical.