Once this is understood, the next point is inevitable.
For what provides the energy to start and maintain the reed's vibration ?
The air flow from the human body.

By blowing on the saxophone a second resonator is automatically connected to the system.
This is the cavity within the body, consisting of the interconnected.
- mouth
- throat
- trachea
- and lungs
Sound waves travel in all directions, regardless of the direction of air flow. Therefore the reed sets up vibrations in both resonators, the saxophone and the human body.
Both resonators send out their own vibrations to the reed. The reed, trying to serve both masters, combines the two directives into one average vibration, which is spread through both resonators.