Olivier Messiaen - Quatuor pour la fin du temps (Quartet for the End of Time)
Messiaen composed this work in 1941 in a Nazi prison camp. It is written for the four instruments that were available (violin, cello, clarinet, piano) and was performed first there by the prisoners. This is certainly one of the masterpieces of the twentieth century chamber music. Very moving. The recording I am listening to now is by Tashi.