Piano Guts !

How does the piano make sounds just by pressing on a piano key?

The inner workings of an upright piano.

1. Pedal.
2. Pedal connection.
3. Exhauster (one only shown).
4. Reservoir; high tension (low-tension reservoir not shown.)
5. Exhaust trunk.
6. Exhaust tube to motor.
7. Air space above primary valves.
8. Secondary valves.
9. Striking pneumatic.
10. Connection from pneumatic to action of piano.
11. Piano action.
12. Pneumatic motor.
13. Trackerboard (music roll passes over trackerboard).

(Resource: Duly Notated / Wikipedia)