The second movement, Moderato con moto, is rather obsessively in triple time. The second theme is more mysterious and dreamlike. Here is the St. Petersburg Quartet:
The third movement, in G flat major but with a strongly modal feel, is one of Shostakovich's trademark passacaglias in which a repeating bass line is added to, layer by layer, with growing intensity. This slow movement, a Lento, is gravely and soberly beautiful. Here is the Borodin Quartet again:
I apologize for the chopped-off ending. The third movement goes without pause into the fourth and in this clip, the characteristic cadence that ends each movement is cut off in the middle! It reminds me of a story about Bach. He went to visit a friend and just as he knocked on the door he heard his friend playing the harpsichord. As the knock sounded, he had just played the dominant, and immediately got up and answered the door. Bach, hearing this, rushed to the harpsichord and played the tonic to complete the cadence! Well, I'm sure we have all done that...
The last movement combines thematic elements from each of the preceding ones into a sonata form in four different tempos. Here is the St. Petersburg Quartet. Remember, it begins with the end of the cadence from the third movement.
After a dynamic development, the movement ends quietly with the ubiquitous cadence. You know, if you slightly distorted the dominant harmony and added a 7th and a minor 9th, you would have, um, lemmeseenow, in G major, D, B, C, E flat. The D is the root of the dominant, you could go from A to B, anticipating the third of the tonic and the C and E flat are the 7th and minor 9th. Why would you do this? Well, as a matter of fact, using German names for the notes, it spells DSCH, Shostakovich's motto. You know, I think that's what he is doing on the dominant in these cadences. I don't have the score, but this is what it sounds like to me: