Trombone The natural frequency of a trombone can be modified by changing the length of the air column inside the metal tube.

Consider the trombone with its long cylindrical tube, which is bent upon itself twice and ends in a flared end. The trombone is an example of a wind instrument. The "tube" of any wind instrument acts as a container for a vibrating air column; the air inside the tube will be set into vibrations by a vibrating reed or the vibrations of a musician′s lips against a mouthpiece. While the speed of sound waves within the air column is not alterable by the musician (they can only be altered by changes in room temperature), the length of the air column is.

For a trombone, pushing the tube outward away from the mouthpiece to lengthen it or pulling it in to shorten it alters the length. This causes the length of the air column to be changed and subsequently changes the wavelength of the waves it produces. So the natural frequency of a wind instrument such as the trombone is dependent upon the length of the air column of the instrument. The same principles can be applied to any wind instrument, whether it is the tuba, flute, wind chime, organ pipe, clarinet, or pop bottle.