Sound is produced on a saxophone when the player produces a stream of air across the tip of the reed, causing it to vibrate. The frequency of the vibration is determined by the distance the air must travel before escaping from the saxophone.
Tone holes are carefully positioned on the body of the instrument to create the best intonation possible for each note. As each key is pressed, its pad (soft leather disk under the key) stops the airflow through that tone hole. The pitch gets lower as the distance the air must travel increases.
The saxophone family includes soprano, alto, tenor, and baritone saxes. Most players begin on the alto sax and then branch out to learn the others.