Here are three obscure but most excellent rock “concerti” from the early 1970s. In addition to the jazz orchestra classics by Frank Zappa, I keep coming back to these three:
Nine Feet Underground (sample but not a typical passage) from In the Land of Grey and Pink by Caravan — 9FU is a progressive rock masterpiece. It rambles through several loosely connected improvisational and lyric “movements” with multiple key changes and unusual time signatures. Available only on CD (there are other live versions as well on MP3).
Atom Heart Mother (sample) by Pink Floyd — AHM is very classical in form and instrumentation. It makes use of a small orchestra and chorus (a sort of “ninth symphony” of rock classics). Available on CD and MP3.
Peaceful World (sample) by The Rascals — PW is a pleasant extended jazz improvisation. One of the nicest musical “grooves” I know of. Only available on CD.
One of the great novels of the twentieth century. Also one of the most powerful expressions of existentialism and humanism ever written. I 
The Plague is an allegorical novel set in the modern city of Oran on the north African coast. The principal character Dr. Rieux confronts a series of medical, ethical and moral dilemmas as an epidemic of bubonic plague breaks out and the city is quarantined. Rieux must overcome his fear, loneliness and despair in order to function while conceding that he is mostly powerless in the face of his microscopic enemy. As the crisis abates he concludes that he only did what had to be done and will be done again “by all who, while unable to be saints but refusing to bow down to pestilences, strive their utmost to be healers.”