What created the problem was the differences between a theme and a melody. A theme can be a short motif, such as the opening of Beethoven's Fifth Symphony, or it can be as long as a Brucknerian theme from one of his symphonies. It is the character of the theme, the way that it can be changed and developed, that made for the success and utilization of sonata form. A melody can be beautiful and complete in itself, but not all melodies can be successfully used and developed in sonata form in a symphony. That is the dilemma that Romantics like Tchaikovsky faced when he began to write symphonies.
Tchaikovsky had a great gift for melody, but he was not the supreme architect like Beethoven who could take a few notes and construct a finely wrought symphonic structure around it. Tchaikovsky's first three symphonies were written in a more strict adherence to sonata form and structure. It wasn't until his 4th symphony that Tchaikovsky wrote a symphony in a very loose symphonic structure. The 4th was not immediately popular, the premiere of it caused much criticism, probably due to the fact that if a regular concert-goer that was in the audience expected a 'traditional' symphony, they most certainly didn't get one. But time has proven that Tchaikovsky's way with the symphonic form allowed him to stay more true to his talent. The three symphonies he wrote in this loose form are played way more often than those first three that are closer to tradition.
The 4th Symphony is in the traditional four movements:
I.Andante sostenuto — Moderato con anima — Moderato assai, quasi Andante — Allegro vivo - The many changes of tempo in this movement tell a great deal about the musical and emotional content of it. This movement alone is longer than the other three put together. The music has vitality and power, with melodies that weave in and out of the loose structure, melodies that are developed, and some that aren't heard but once. Tchaikovsky's newly discovered way to write a first movement for a symphony fits his musicianship and temperament very well. There is always drama in Tchaikovsky's music, and this movement runs the length of emotion from calm reserve to borderline hysteria.
II. Andantino in modo di canzona - A beautiful melody is played and configured, with a central section of reflection on things already heard that builds into climax that is related more to the first movement than this one. The opening melody is heard again and there is more of a darkness to it now than the beginning. The music slowly and gently comes to a quiet close.
III. Scherzo: Pizzicato ostinato — Allegro - One of the most original orchestrations of a master orchestrator, this movement hears the strings playing pizzicato throughout. The winds pick up after the opening and play a tune until the brasses interrupt with a marching tune reminiscent of Tchaikovsky's ballet music. The strings return as in the opening, then enter into a dialog with the winds, the music is again interrupted by the marching brass, the pizzacato strings return and end the movement on a quiet note.
IV. Finale: Allegro con fuoco - The movement begins with a clash of cymbals and a rollicking tune. After that, Tchaikovsky quotes and old Russian song, In the Field Stood a Birch Tree. The tune is repeated a few times with different instruments, the first theme that began the movement returns until the orchestra carries on with variants on the old Russian song. A direct quote from the beginning of the first movement interrupts the proceedings and leads back to the opening of the movement. Snatches of the old Russian folk song are heard and the orchestra whips itself into a grand ending.