I do quite a bit of bounce flash too, so I found this question quite interesting.
My go-to is bouncing off the ceiling, as they’re (normally) at least somewhat close to white. In your case with a vaulted ceiling, I’d still give it a try, but you’ll wind up with two likely problems: Firstly it might be too far away to get enough power from your flash. Secondly, you’ll wind up with the light coming almost straight down from above, leaving black holes where the harpist’s eyes are supposed to be. With that in mind, I’d be inclined to turn the flash around, and bounce off the ceiling as far behind me as possible. This will at least give you an idea how much light you have. (Remember the modified exposure triangle for flash?)
Personally, my next go-to is to find any other surface I can bounce light off. As close to white or grey as possible. (don’t forget you can turn the flash around and over your head to bounce off a wall behind you) In the case of your golden wall, I would give it a shot and see what happens to my colours. Obviously, you can adjust colours in post, but the danger is this: If you create a strongly yellow light from the wall and adjust in post to make it look neutral, the light coming in from the window will turn out looking very, very blue.
As you mentioned, you can take the flash off camera. This give you a whole new level of flexibility. You can move your flash to another place where there’s something to bounce off of or through (think light curtains or lampshade) Alternatively, and this is a little more fussy, you can put the flash off to the side straight onto your subject and experiment with angles of hard lighting