It begins with a long slow movement featuring a somewhat twisted theme, ending with a pseudo-baroque trill. The second movement is a scherzo and the third a wild galop that almost reminds one of Rossini.
Some of the tension of the first movement of this symphony can be explained by the fact that while Shostakovich may have achieved a reprieve with his 5th symphony, the purges of Soviet society continued without letup. Prominent writers and other figures were brought to trial on trumped-up charges. The great poet Osip Mandelstam was arrested and sentenced to five years hard labor--conditions were so harsh he perished after a few months, in December 1938. The friend of Shostakovich, Vsevolod Meyerhold, an important actor, director and producer, was tried in one day and shot the next. Despite all this, Shostakovich was eager to get to work on his next symphony. A number of different plans were conceived and rejected, including a monumental work for chorus and soloists on the theme of Lenin. By the end of August enough was completed for him to play excerpts for some colleagues on piano and the instrumental version we know was coming to life. The music was finished in October and Shostakovich said he was particularly pleased with the last movement and its themes of "spring, joy, youth, lyricism." The first performance was a success and the finale was encored. Some critics were troubled by the lop-sided layout and it did not entirely fulfill their expectations. Mind you, the 5th symphony was a tough act to follow and at this point Shostakovich may well have felt that any symphony premiere that did not result in being sent to a labor camp was success enough!
Russian theorists have often looked at Shostakovich's music from a modal point of view and the main theme from the first movement of this symphony has been described as "lowered Phyrgian mode". Others have noted the presence of the octatonic mode, which alternates whole and half steps. These and other Russian modes often have a Phyrgian feel to them because they typically work by lowering several notes of the scale below where we normally expect. The great bulk of the theoretical work on Shostakovich has yet to be done and most of what has been done is in Russian only! But I expect, that, given the continued interest in Shostakovich, we will continue to work out some of how he constructed his music. For now, let's listen to the whole symphony: