This anime character is dancing to the music thanks to some animatronic tricks which [Scott Harden] put together. She dances perfectly, exhibiting different arm and head movements at just the right time. The secret to the synchronization is actually in the right channel of the audio being played.
The character in question is from an Internet meme called the Leekspin song. [Scott] reproduced it on some foam board, adding a servo to one arm to do the leek spinning, and another to move the head. These are both driven by an ATtiny44. All of the movements have been preprogrammed to go along with the audio track. But he needed a way to synchronize the beginning of each action set. The solution was to re-encode the audio with one track devoted to a set of sine wave pulses. The right audio channel feeds to the AVR chip via an LM741 opamp. Each sine wave triggers the AVR to execute the next dance move in the sequence. You can see the demo video for the project after the break.