In a tube (open at both ends) that's vibrating at its fundamental frequency, is the air pressure the ambient air pressure at both ends and higher in the middle, lower in the middle, or can it be either higher or lower in the middle? Why? If the same tube is vibrating at the frequency of its second overtone (1/3 the wavelength of the fundamental frequency), can the pressure be the ambient pressure at one end and either higher or lower at the other end? If you blow on one end, does that end become the one with the regular pressure or the higher/lower one? If one end of the tube is blocked, does its fundamental frequency then become half of what it was before? String instruments seem so much easier to understand than wind ones.