The composer's six symphonies can be seen as two complementary ensembles that, although quite different, participate in one and the same all-embracing universe.
The first three, less well-known, overflow with verve and imagination - like the first subtitles given to the movements of Symphony No. 1 "Winter Dreams". Dance is never far away in these three works that precede the final three "great" symphonies, marked by the fatum. Within these two sets, the Third possesses all the characteristics of a transitional symphony: linked to its two forerunners, it dynamites the sequence of ideas and prepares the way for the Fourth. The Sixth, whilst retaining the introspective tones of the preceding symphonies, marks a terminal attack on the obsession with fatality.

The spirit of dance is inseparable from Tchaikovsky's work. With its five movements, the Third Symphony has a suite-like feel to it, whilst the Fifth gives birth to a waltz and the Scherzo from the Sixth is a march that leads us towards ballet. The second movement of the Sixth Symphony, in 5/4 time, is a false and unresolved waltz: a waltz lacking one beat...

The three great symphonies do not only underline Tchaikovsky's exceptional mastery of composition: his own autobiography, equally omnipresent, unfolds its theme of destiny. This fatum begins in the Fourth Symphony with underlying brass and horns from one end to the other. At the close of the Fifth Symphony, the subject returns in the finale as an ultimate triumph, in the major key. In the manner of a "leitmotiv", destiny is transformed in the Sixth "Pathetic" Symphony into a desire for death. Playing with his fate, Tchaikovsky consciously becomes deathly sick. The retrospective structure of his last symphony is framed by the theme of the Russian Orthodox Requiem, both in the first movement's development and at the very end of the work.

I chose to bring together the third and sixth as they represent milestones in this symphonic ensemble. The second and fourth share a proximity in writing (one rewritten in 1879 reflects the other created in 1878); the first, the most imaginative, and the fifth, the most positive, constitute an introduction to the cycle.
The first two symphonies bear a clear resemblance to Schumann's work on a poetic level (think of Carnaval, and Scènes d’enfants...); a form of simplicity found in The Nutcracker which is also in some ways very Schumannian. The Third Symphony opens with a funeral march and ends with a polonaise, reminiscent of both the polonaise in Eugene Onegin and Schumann's Violin Concerto. His developmental technique is fairly Beethovenian, but more spontaneous, with something more emotional.
There is also a Slav side to Tchaikovsky, darker, more painful, deeper and more condensed than Robert Schumann. I would also mention Mahler along with Schumann: the three composers share a kind of genealogy of composition, no doubt linked to the constructive inner chaos of their work.