Three of us have just finished the first complete draft of our first attempt at collaborative fiction. While the plot and the story are tightly knit, we have are facing trouble in maintaining the tone of the narrative. Any advice?
Give each collaborator free rein to edit any part of the story for tone. After a round or two of that, you won't be able to tell who wrote what.
If it's a multiple POV story, you can give each POV to one collaborator to edit for tone. That way, if tone varies, it gives each character a distinct voice.