Your connector is riveted to the name rail. Take a hand drill, and drill out the rivets. If the rivet is not a pop rivet, there will not be a convenient center hole to guide your drill bit. Smack the head of the rivet to give yourself a little flat surface, and then smack it again with a center punch to make a dimple to guide your pit.
Take the name rail off the piano, then.... Take an 1/8-inch drill bit, and drill through the center of the rivet, right through the panel. If some portion of the rivet remains, fight it with needle-nose pliers, or just pick at it with a nail.
If you are a real brute, and you don't have a drill handy, you can sometimes break the back side of the rivet off with pliers, and then force the barrel of the rivet back through the front side of the hole. Don't try to push with a nail, because it will spread the rivet and make it tighter. Either use the head of a finishing nail; or clip the point off a nail, and use that. This isn't really a nice way to treat your piano, and it is not the best way to remove the rivet cleanly. (The drill will do a clean job.)
sean