The Schumann is one of the nicest pieces of chamber music and one of my favorites. I'm not a big chamber music fan, but this is one very fine piece - the quartet was very good and I really like Pressler - and there is something about his facial expression that is fascinating to me - he often turns towards the quartet and audience while playing so you get it see it quite a lot.
The middle piece was String Quartet No. 3 by R. Murray Schafer, a Canadian composer and sound researcher. His pieces are quite extraordinary. The first movement open with the cellist on stage playing a bass note on one string and then adds a second note a quartertone or less away and this continues for quite a while with minor variations or a slow theme. It was interesting listening. Then you can hear a higher string and soon the Violist walks from back stage playing and soon joins the cellist. Later one at a time the two violins come down the two aisles playing and join the crew on the stage where they continue the movement.
The second movement is a complete contrast. They all play extremely vigorously and accompany themselves with lots of vocal noises. The composer says "like the vocal shouts of karate". Some of it sounds like dog barking, there are lots of repetitive sound patterns some very noisy and some quiet such as that caused by popping their mouths. All of this while playing the dissonant lines on their instruments. The final movement is a complete contrast and is calm and peaceful. Apparently all of his compositions are over the top and I read it is difficult to decide whether to classify his work as music or stage.