* Vary the length of the flute. The longer the flute, the lower the frequency of the sound it produces. This is because the longer the flute, the longer the air column inside the flute, and the slower the air molecules can vibrate.
* Vary the diameter of the flute. The wider the flute, the lower the frequency of the sound it produces. This is because the wider the flute, the more air molecules there are inside the flute, and the slower they can vibrate.
* Vary the embouchure. The embouchure is the way the player's lips are positioned on the mouthpiece of the flute. The tighter the embouchure, the higher the frequency of the sound it produces. This is because the tighter the embouchure, the faster the air molecules can vibrate.
In addition to these three main factors, there are a number of other factors that can affect the frequency of a flute, such as the temperature of the air, the humidity of the air, and the type of flute being played.