What constitutes a valid reason for showering and shaving during the nine days? Am I allowed to perform activities which will force me to shower afterwards? May I practice a musical instrument?

I write this response after Tisha B'Av and I hope therefore that the question and its reply will remain theoretical- that by next year G-d will complete the redemption and the Temple will be rebuilt. One is allowed to shower to remove sweat and body odor in water that is not so cold as to be painful. One can exercise or engage in sports, or work at physical labor even though as a result he will sweat. One can practice a musical instrument not for pleasure until the week of Tisha B'Av itself (Shu"t Tzitz Eliezer XVI 19).