To clarify, I don’t mean ‘‘how to do put a different key signature’’ but rather to, for example: I have a piece written in C major, and I want to apply a key signature change to the start of the piece to C minor, and making all E’s, A’s and B’s flat, as the key indicates. If I do this the usual way, the key signature changes but all the ‘‘old’’ music content doesn’t get updated with the new accidentals but rather they keep the natural E’s, A’s and B’s. I’d like to know if there is a way to automatically apply a key signature to already existing music content while forcing the new accidentals onto the old music content so it conforms to the new key signature, that way I could easily make a whole piece switch between parralel modes of C, for example and check how it sounds. Right now the only way I know is to change the key signature and then manually changing every single note of the piece, which is obviously an impossible task when it comes to lengthy pieces.
I’d also like to ask how to easily transpose music content by intervals? Say something like ‘‘select music content>>tranpose…>>descending minor 3rd>>Apply’’. This combined with what I asked above would help me easily and quickly tranpose among different keys and modes.