Guys! Here's one of my favorite tips to get the throat to relax during singing.
Begin with a medium-light resistance band, holding it with both hands horizontally (with about 6-10 inches between your hands) at about sternum level.
Vocalize on a glide from low to high while moving your hands apart simultaneously. This is to simulate an internal stretch in your vocal tract.
This can be done on any vocalise of your choice, or even a part of your song. It becomes more difficult to use your throat to support your sound when you are engaging your body in this way.