Cardcaptor Sakura - Season 3 Episode 3 Sakura and the Dangerous Piano

Exhausted from the events of the other night, Sakura remains in bed and sleeps into the afternoon before being visited by Syaoran and Tomoyo. Kero explains that Sakura used a great deal of power to transform the Clow Card, explaining her sudden tiredness. Since the Fiery Card was transformed to be under jurisdiction of Sakura's power, Sakura's friends henceforth transform the cards into "Sakura Cards". Later at school, Sakura overhears Eriol playing the piano and has Tomoyo sing to his music; unbeknownst to them, however, Eriol enchants the piano while he plays.