I probably have a lot of nerve answering this question, but it seems to me that when you are in a key with sharps, you would express an augmented interval as a sharp. A diminished interval too. Or is that not what you meant?
Hi Alison, Could you please indicate where this hard and fast rule resides? I have to say that in all of the years of study I’ve put in, I’ve typically found that there is a relationship between tempo and duration, and that the difference can be and sometimes is reflected in the printed version of pieces.
As with so many musical questions, I wonder if there is some theory book that says “hard and fast” and some other music theory book that says maybe ok in one version or another.
Kodaly makes a major issue of teaching duration as being totally divorced from tempo, but I can’t remember any references to the printed note.