Open your throat or get your throat open!
Well, this little phrase does have some important truth to share with us in singing. Think about it. If our throat was closed, then we would not be able to breathe or swallow or sing. The throat being closed is just another way of indicating that there is some sort of constriction. We do not want throat constriction when we sing.
So, open your throat seems like a good idea, something a teacher might say to a student. However, this is not a helpful phrase of instruction. Oddly enough, when one tries to “open” the throat, the throat becomes enlarged beyond what it should be for the pitch being sung. Sometimes this over-enlargement combines with a subsequent forced lowering of the larynx. All of this creates unnatural rigidity in the throat, not constriction per se. But still, there is now unnecessary tension that is just as bad as constriction.
Rather than trying to “open the throat,” let us work on the development and coordination of the vocal muscles and there will be no constriction nor unnecessary tension. The throat will be open as much as it needs to be without the singer trying to unnaturally open the throat.
One could say that the “open throat” is really a feeling of no-feeling; meaning there is no constriction and therefore the throat is open. When it is open we don’t even notice it. It just is, natural and free with nothing direct or overt to do!