Music notation and vacuum pump: what they have in common

1. Step 1. Music notation — is used in — Player piano. The rolls encode notes.
2. Step 2. Player piano — has part — Bellows. Pedal bellows create suction.
3. Step 3. Bellows — has part — Check valve. An air intake valve.
4. Step 4. Check valve — is part of — Vacuum pump. Valves stop air from flowing back.

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