Listen to Not Entered: String Quartet No. 15 in D Minor, K 421 - I. Allegro Moderato online. Not Entered: String Quartet No. 15 in D Minor, K 421 - I. Allegro Moderato is an English language song and is sung by Brainwave-Sync. Not Entered: String Quartet No. 15 in D Minor, K 421 - I. Allegro Moderato, from the album Classical Music: Strings with Brainwave Entrainment, was released in the year 2012. The duration of the song is 7:42. Download English songs online from JioSaavn.