When writing music in a mode that is not major or minor, do you preserve the key

[LawMan]

signature and tweak the notes? Say you are writing in the Mixolydian Mode, then is it best to keep the key signature for Major and just lower all 7th scale degrees manually in the music instead of modifying the key signature?

For the Dorian Mode, does it make sense to keep the key for Minor, but just raise all 6th scale degrees manually in the music instead of modifying the key signature?

The reason I ask is because, don't we want to preserve the key signature in the sense that we want to be able to tell what key a piece of music is in by looking at the key signature?

 

[Rachel_Not_Idiot]

I would fit the key signature to the mode. For example, if I was in the C Phrygian mode, I would have 4 flats in the key signature. The key signature is not the only way of determining the pitch centre of a piece, and having too many accidentals makes music cluttered and more difficult to read.