The phenomenon where the sound in a musical score differs depending on the instrument is primarily due to the concept of "transposing instruments." Transposing instruments are those where the note ...
I suggest disabling the display of the key signature in the case when the user changes the instrument (transposing) to another, and when the score is shown in concert pitch. It's one thing when the ...
When using the Replace Instrument function to change a transposing instrument to non-transposing the instrument is changed, but not the transposition.