1. Changing the length of the instrument: Changing the length of the trumpet's tubing changes the frequency of the sound waves produced, and thus changes the pitch. This is done by pressing different combinations of valves on the trumpet, adjusting the length of the tubing the air travels through. There are three valves on the trumpet, and each valve increases the length of the instrument by a different amount, which lowers the pitch by a different amount.
2. Changing the players embouchure: The player's embouchure, or the way in which they shape their lips and mouth, also affects the pitch of the sound produced. By changing the shape of their lips, the player can "lip" notes higher or lower within a certain range, even without pressing the valves. This technique allows for micro-adjustments in pitch and for playing notes in-between the notes dictated by the length of the tubing alone.