Diaphragm and plough: what they have in common

1. Step 1. Diaphragm — is part of — Drum. A diaphragm.
2. Step 2. Drum — is made of — Leather. The drumhead is stretched hide.
3. Step 3. Leather — is material for — Horse collar. The collar and traces are leather.
4. Step 4. Horse collar — is used in — Plough. The horse collar made ploughing with horses possible.

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