I think the "too trivial" edit suggestion reject reason was removed precisely because there is no such thing; if a post is better after the edit, even marginally, then the edit should be approved.
Stack Exchange is a collectively maintained repository of knowledge, and every small part helps.
As for this particular edit and question however, it could be argued that the question itself is off-topic, and deserve to be closed. Rejecting the edit could give that signal to the original editor, and might be a worthwhile thing to do.
"Sounding terrible", apart from being completely unclear, can be related to any number of reasons, all of which would be guesses on any answerer's part. It would seem however that rules are a bit looser on music.se than on other sites I generally consult, so possibly this is more litigious. All the same, a small edit is still an improvement.