Weird question - in singing, how much is opening your mouth wide mechanical vs. aesthetic? So, like, I was noticing in this harmony, you can barely tell at a distance that their lips are moving: https://www.youtube.com/watch?v=i-u7yPTDOQ4
Makes sense, since it's a somber tune. It's also hard to imagine e.g. Frank Sinatra opening his mouth wide. Whereas of course in pop or rock, you have to unhinge your jaw.