The original compression wave, now greatly reinforced by the second 'puff' of air, sets off on another two trips down the pipe (travelling four pipe lengths in total) before the cycle is repeated again.

In addition to this primary compression wave, other waves, known as harmonics, are created. Harmonics are caused by factors including the imperfect wobbling and shaking of the reed, the reed sealing the mouthpiece opening for part of the wave cycle (which creates a flattened section of the sound wave),