This excerpt is from Louis Armstrong's first autobiography, published in the 1930's. The introduction was written by Rudy Vallée, who was a very big deal crooner back then. I use the last line of this quote all. the. time. Some dance clips I can watch once and I'm good. Others I need to watch over and over again.
""...try playing it a second, third or fourth time, and eventually there must dawn on you that this man knows what he is about and you will begin to feel upon you the sway of his extraordinary musical personality. It is a test of artistic work- repetition with a growth of effect."