I just played a Yamaha student horn and it's better than my Marcinkiewicz at slotting high notes. I am wondering whether the main slide water key (I have the kind that looks like a little tube and you press a button to make the condensation come out) is affecting the performance of my horn. I think that it is plugged up somehow, I press it and then nothing comes out, but the trumpet still gargles, even after I hold the button down and blow. So I have to take out the main slide and physically empty it out... Could the water key malfunctioning be a factor in the trouble slotting? This is a random shot in the dark here, but would mouthpiece weights, valve caps or anything else increase the slotting ability of my Marcinkiewicz?