Here's why:

* The Reed: The shehnai's reed is a thin, double-layered piece of bamboo that is held in the player's mouth. When air is blown through the reed, it vibrates, creating the sound waves that are amplified by the instrument's body.

* The Body: The body of the shehnai acts as a resonator, amplifying the vibrations of the reed and creating the distinctive, rich sound of the instrument.

So, while the entire instrument is involved in producing the final sound, the reed is the primary vibrating element.