Being a musician is a very physically demanding art. While having good technical skill to master hard music is great, if you don’t have control of your body to accomplish the most important aspect of performance – the emotion – your performance will not be so unlike a computer generated version.
The best performers out there are great not because they are masters of hard music, but because they have learned to exercise exceptional CONTROL of their body; when to hold a pause 2 seconds longer before lifting their hands from the keyboard, how to train the muscles in their hands to do perfectly spaced 32nd notes, and how to not rush a fast song, how to control a vibrato, and how to steady that bow on a string and hold it until the very last drop of sound fades into the air.
Want to be an extraordinary performer? Learn absolute fine-tuned body control. Muscle training through strengthening and condition. Practice doesn’t make perfect, but perfect practice does.