  The mechanical properties of the human lip between relaxed and fully
contracted are not enough to explain the full range of professional brass
players. Brass players manipulate their mouth cavity and vocal tract which act
as Helmholtz resonators driving the lips. Brass players increase their upper
ranges by reducing the amount of lip mass that vibrates using upstream or
downstream techniques. In addition, it was found that the cup of the mouthpiece
is a separate resonating cavity: not just an extension of the instrument
funneling air down the length of tube. For the lowest three octaves of the
range, the trombone does not act as a tube with a standing wave resonance, but
as a transmission line responding to a string of pulses produced by the lips.
