How do composers write music for each instrument if each instrument is limited by musical scales?
But trumpets and flutes can play chromatic scales! So they simply transpose the key (in your example, if the actual key of the music was C, the trumpets would be reading in D and the flutes in A). However, it used the be the way you describe – I think flutes have been chromatic forever, but trumpets (and other brass instruments like horns) used to be able to play in only one key. So the performers did have to have instruments in multiple keys, and never had accidentals in their parts. They didn’t play very much though… usually a few notes with the timpani and that’s about it. You’ll also notice that older music is all written in the same few keys; C, D, B-flat for example. You didn’t see key signatures like G-sharp minor in those days, because nobody had a trumpet that could play it!
