Harmonics are notes that are higher than the designed capabilities of the instrument. In effect, they extend the range of your saxophone. The above ten fingerings are all I use myself, though it is entirely possible to go much higher. There are many alternate fingerings for the above notes; your reed/mouthpiece setup could drastically alter the situation one way or the other. It is not an exact science, so experimentation is the key. Using harmonics, however, does require a whole new practice regime - not to mention a whole new and are not for the faint-hearted!