Frequency: At any point in the air near the source of sound, the molecules are moving backwards and forwards, and the air pressure varies up and down by very small amounts. The number of vibrations per second is called the frequency (f). It is measured in cycles per second or Hertz (Hz). The pitch of a note is almost entirely determined by the frequency: high frequency for high pitch and low for low. Human ears are most sensitive to sounds between 1 and 4 kHz - about two to four octaves above middle C. That is why piccolo players do not have to work as hard as tuba players in order to be heard.
The lips control the air flow: Brass players can make musical sounds with just their lips. This is one of the first things a brass player learns: you close your mouth, pull your lips back in a strange smile, and blow. The result may be anywhere between a low pitched or a high pitched musical note, depending on the tension in your lips and other parameters.
Since I am a current trumpet player in the Symphonic Band for our High School this part of Physics truly relates to my everyday life.