In a brass instrument, the fundamental is fixed by the length of tubing
(alterable by means of valves (trumpet, tuba or French horn) or by
moving the slide (trombone). The harmonic that is heard above that
fundamental is determined by the vibrations of the players lips. By the
way the fundamental is never heard, the player plays at least the 2nd
harmonic (ovtave and a fifth) above the fundamental.
My understanding of the woodwinds, is that the fundamental is fixed by
the length of the tube and the holes that are open or closed. The role
of the reed, or flute mouthpiece, is to set the columns of air
vibrating. The diferent sounds of these instruments are caused by
different amounts of the upper harmonics, that being controlled largely
by the type of reed or moutnpiece, but to some extent by the skill of
the player.
Jerry EPstein