Top of the Tongue - Tip or Convex Blade?

Your tongue blocks two holes in the center, leaving the left and right holes open when performing an octave (1+ C and 4+ C for example). You can either use the tip of your tongue to block those two holes or use the tip-top of the tongue (called the blade), by using an ultra-light touch so that the natural convex shape of the tongue doesn't flatten out and cover too many holes. Give this light touch a try and I'll discuss some other interesting advantages of this light touch technique tomorrow.