Q. Please explain the Physics of "Bending"

[Rich_E_Dowey@xxxxxxxxxxx]

     I'm sure this subject has been covered before, but I'm having trouble 
     finding the thread in the 33 + months of archives.
     
     What actually creates the effect of bending? Not what you do with your 
     mouth or lips etc.. but is it an enlarged embrouchure or some other 
     physical characteristic that actually creates the effect of bending?
     
     Please keep the answers as *simple* as possible, my brain hurts 
     already.
     
     Rich