I studied Tanner's serve in the '70s because at the time he had the ultimate serve. To this day his serve still stands as one of the cleanest and simplest, and thus very reliable and effective. He could probably put serves into the service box with his eyes closed. An extra benefit of his shorter and simplified motion was that it never broke down in difficult conditions since the toss was less vulnerable to wind movement and also gave him an edge when serving into the sun thanks to a lower more efficient toss. What I learned back then is echoed in his words now. Toss to the highest point of your extension, strike it at the apex before it begins to fall, and coordinate your motion so that it's continuous making it a very fast delivery often mesmerizing an opponent used to long rhythmical motions. The net effect is not only more velocity on the ball but a much shorter interval between the beginning and the end of the motion. His opponents always felt rushed when he was serving.
In his own words at CongruentTennis.com
