Every singer has three or four or five techniques, and you can force them together in different combinations. Some of the techniques you discard along the way, and pick up others. But you do need them. It's just like anything. You have to know certain things about what you're doing that other people don't know. Singing has to do with techniques and how many you use at the same time. One alone doesn't work. There's no point to going over three. But you might interchange them whenever you feel like it. It's a bit like alchemy.