Listen to Piano Concerto No. 15 in B-Flat Major, K. 450: I. Allegro online. Piano Concerto No. 15 in B-Flat Major, K. 450: I. Allegro is an English language song and is sung by Baby Music. Piano Concerto No. 15 in B-Flat Major, K. 450: I. Allegro, from the album Classical Melodies to Calm Baby – Soothing Baby Music, Rest with Classical Music, Kids Relaxation, was released in the year 2017. The duration of the song is 2:47. Download English songs online from JioSaavn.