Priscilla Villanueva is tired of practicing piano when all her friends are outside playing. Discouraged and bored one autumn day, Priscilla opens her sheet music and begins playing a challenging sonatina. Unfortunately, it is not long before she smashes her fingers against the keys in frustration. But when her fingers suddenly stumble upon a sticky A key, everything changes.
After a beautiful, twirling column of colors rises from the piano keyboard, Priscilla falls off her bench in surprise. As a translucent man dressed in a tuxedo appears before her, the ghostly spirit who calls himself Pythagoras tells a shocked Priscilla that she is a talented musician who has just lost an important element that he can help her find. Soon, he begins to teach Pricilla interesting information she never knew about musical history and theory.