The pressure waves constructively add together to create a louder sound. As the musician presses the valves and lengthens the trumpet tube, the oscillation slows and the trumpet s pitch goes down. The frequency of oscillation depends on the length of the trumpet tube. The frequency of oscillation increases. The air is traveling about faster.
Lighting occurs when large amounts of electric charge flow between the clouds and the ground.
Like charges repel, they do not attract. The atmosphere does a great deal of work in creating the separated charge that produces lightning. Show that it takes work to move positive charge from the negatively charged ground to the positively charged cloud overhead. Oppositely charged particles attract each other and it takes work to overcome that attraction when separating them. One indication that this dangerous charge accumulation has occurred is that your hair begins to stand up.