A Chrome extension that nightcores YouTube videos on the fly.
Nightcore is an artist from Norway that, in 2002, released albums of dance tracks with elevated pitch and tempo. Due to its wonderfulness, ease of production and the advent of YouTube, these style tracks slowly gained popularity. Today, nightcore is a music metagenre—any song whose pitch and tempo has been raised, often along with an anime image and almost excusively distributed through YouTube.
Here's an example: Nightcore - Everytime We Touch [Cascada]
It just uses the Web Audio Api to let you raise the pitch and tempo of a YouTube video's audio as you watch.