You can learn a lot about engineering and acoustics just by taking a look inside a music box. The tiny instruments were first developed in the 18th century and peaked in popularity during the 19th century, before being replaced by the phonograph and radio in the 1900s. In the short tutorial above, engineer Bill Hammack peeks inside a traditional music box, explaining the complex feats of engineering that go into the device’s rendition of a basic tune.

Hammack, who goes by the YouTube moniker “Engineer Guy,” has a whole series of educational videos, which explain the underlying engineering principles behind everything from film projectors to the ill-fated RMS Titanic. In order to make “How A Wind Up Music Box Works,” Hammack decided to take apart a music box and figure out how it worked on his own. After studying each piece, and filming the device in slow motion, he managed to figure out the exact role played by each tiny screw, cog, and pin. The video reveals the results of his inquiry, explaining the simple-yet-brilliant mechanisms that control the pitch, speed, and volume of a music box's song.

[h/t: Gizmodo]

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