This movement, in E-flat Major and marked “andante con moto”, is in 3/4 time, but he fills in the eighth notes, which makes it a kind of slow minuet. It’s in ternary format. The strings take the theme while the piano plays an eighth note underlay.
At 3:45, the middle section, marked “animato”, is a march in 3/4 time and C Major. Schumann and Brahms knew how to make something like this work. It’s a march of little tin soldiers, and it’s charming. (When Arnold Schoenberg orchestrated this quartet, he turned this middle episode into a march of the local Storm Troopers through the Jewish quarter of town; it’s in really bad taste.) Then it jumps into A-flat before settling back to C Major.
At 6:03, it disintegrates and returns to the first section via C Major.
At 8:51, the coda wraps it up with the violin soaring into the stratosphere. That tune will just break your heart the way Stern plays it.
Thanks Prof for the chamber music! *Hugs*