I have trouble deciding what accidentals to put in the key signature for pieces in dorianDorian, phrygianPhrygian, lydianLydian or mixolydianMixolydian modes. There seem to be tradeoffstrade-offs associated with each choice.
For example, when writing in G mixolydianMixolydian, setting an empty key signature makes it look like C major or A minor. Having the F# in the key signature forces me to put accidentals all over the piece to mark F naturals.
I prefer to use (in this example) the key signature of G major and natural signs on every F, especially when writing for choir. Singers with varying reading skills will often unconsciously assume that if the piece has G as the tonic, then it is in G major. The natural sign on every F will help them remember there is something special about it.
Is there any kind of convention to follow?