system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What actually happens when your voice cracks?
gpt
Play a guitar string. Now coat that string with snot and play it again. Now press slightly as you play it. Then again with snot covering it. More importantly, stretch that string (turn the peg back and forth) while plucking it. That's what the muscles do. Just like your legs get tired, so do those muscles.

The different Things inside you at any given time affect the vibration of your vocal cords. Muscle strain also does. 

Unless you mean when your voice _changes_ in puberty. In which case, turn the tuning peg while you strum the string. The vocal cords are literally changing.