A "headset" is the result of the rest of the horse being able to do the work in a balanced way; with rider. During transitions, up, down and lateral. It is the Finished Product. We see plenty of horses that were started with trying to set the head first. It's so common now a days it seems to be the norm. So sad. I did it myself, years ago. They learn to not move the head one inch while the rest of the body is a discordant mess.