You guys are talking Beethoven. Here is a short list of some less well-known, but wonderful classical music:
Piazzolla, Oblivion
https://www.youtube.com/watch?v=fKGEpCAciTo Borodin, String Quartet No. 2, Movement 3
https://www.youtube.com/watch?v=CTPrcBAq28Q Kabalevsky, Violin Concerto in C Major -- a listenable atonal work
https://www.youtube.com/watch?v=onIjUnLFmeM