Listen to Cello Concerto No. 2: I. Improvisation - Allegro non troppo online. Cello Concerto No. 2: I. Improvisation - Allegro non troppo is an English language song and is sung by Gregor Horsch. Cello Concerto No. 2: I. Improvisation - Allegro non troppo, from the album Rontgen: Cello Concertos (Complete), was released in the year 2013. The duration of the song is 5:45. Download English songs online from JioSaavn.