Burrundi: Beethoven

Burundi issued this mini-sheet of four stamps in 2011. Mine happens to be imperforate; a perforated version is available. The sheet is called "Composers" and shows portraits of Mozart, Beethoven, Vivaldi, and Chopin. The image of Beethoven includes organ pipes in the background. There is not quite enough detail to the rendering for me to determine if this is a specific instrument or not, and if so what instrument it might be. The sheet's selvage includes more images, presumably of (other) composers, though I cannot determine who they are. LR may be Liszt. UR looks somewhat like the Bach statue in Leipzig.