Here is a youtube recording of the Guarneri Quartet playing one of Mozart’s most well known quartets. Here you’ll hear one of the greatest conversationalist composers ever. What do I mean when I say “conversationalist composer?” I mean that the voices in his music sound as though they’re talking to one another. At the 1:15 mark of the first movement, you’ll hear the leader of the quartet opine an optimistic little idea, and he is joined by the other violinist and the violist at the end. At the 4:58 mark of the same movement, it sounds like the cellist and the first violinist are competing to see who can get the idea to it’s summation. Who can go higher? This theme with the competing character is then used pretty prominently in the development theme, which begins immediately. You find writing like this – where the voices are talking to each other, and working together in a much more cohesive way than a “theme and accompaniment” style – all over Mozart’s mature period, and I love it.
Another personal favorite of this quartet for me is the Trio of the third movement (3:00 of the third clip), where the viola takes over the bass line so that the cello can play a beautiful melody. This kind of instrumentation became very commonplace after Mozart, but he was one of the first composers to give the viola the bass line, and it creates a more intimate color than having the big sonorous cello filling out the basement of the group.