When playing for a long time for example rehearsing with the band and the playing is tough I come to a point where the pitch of my tone rises. What I mean is when tuning in the beggining of the rehersal and then if we try to tune later when Im tired the pich is much higher when my chops are gone..forcing me to pull out the tuning slide a bit. This happens to some of my friends also. How about you? Is this a common thing? And why does it happen? If I had to guess my self Id guess it is due to tension....comments?