There is zero reason to have 2 gamemasters at the same time. There is no rules for their different abilities or different goals. It will be cool, if the author will expands this idea in the future.
Viewing post in The Voice in the Woods comments
The 2 GMs is great idea, I agree. But there is no rules or mechanics or tools for GMs to make it something unique. You can, just, play DnD with 2 GMs, but there is also no reason for that. And in "The Voice in the Wood" there is nothing what 2 GMs can make better then 1 GM.
Don't get me wrong, the game is very good and fun for the evening, thank you for that! This is just a question that comes after the game in my group.