Listen to Piano Sonata No. 13 in B-Flat Major, K. 333: I. Allegro online. Piano Sonata No. 13 in B-Flat Major, K. 333: I. Allegro is an Unknown language song and is sung by Mental Focus Music Academy. Piano Sonata No. 13 in B-Flat Major, K. 333: I. Allegro, from the album Study with Mozart – Greatest Classical Music for Concentration, Increase Brain Power, Focus on Learning, was released in the year 2015. The duration of the song is 2:39. Download Unknown songs online from JioSaavn.