Yes it is a serious question and I was not trying to be a jerk about it in my earlier post. I put that out there because, I believe, most people will agree that the Ravel Piano Concerto in F is usually performed too quicly to cleanly single tongue or it is performed to slowly to cleanly double tongue. So, what would be the limit? The old recordings of Clarke are impressive as are the not as old recordings by Andre. However, once a speed limit has been established and everyone has finally caught up to it, someone else will come along and set a new speed limit. I say this next item will total sincereity and please someone correct this if it is too far off the deep end or really wrong. Maybe a medical doctor will be able to answer this for the following reason: The electrical impulse within the human body is limited in order for the impulse to leave the brain and cause the muscle to move without causing a "misfire", at least that is the way I am understanding how nerve impulses work. Therefore, would the speed of the tongue movement be limited to the the speed of the electrical impulse and the speed at which the muscle (tongue) can respond to that impulse? Again, any MDs out there, please correct, enlighten, what ever if this is too far off the beaten path.