The first movement of Sibelius' Symphony No. 5 begins with a gentle call from the horns, setting the tone for the rest of the piece. The main material of the A-group is introduced by the first horn, while the other horns play long notes below. This unique opening sets the stage for the exploration of themes and motifs that will follow throughout the movement.

The B-group begins at measure 18, introducing a new theme that is developed by the woodwinds playing sixteenth-notes in parallel third motion. This adds a rhythmic layer to the music, with a characteristic 'long-short-short-long' pattern. The second theme takes over around measure 9, and this marks a shift towards a more energetic and driving rhythm.

One of the most disputed points about the first movement is whether it can be considered as having two expositions or not. Some musicologists have suggested that there are two distinct sections to the movement, but Sibelius himself seems to have viewed it as a single, cohesive piece. In fact, he published and performed the first movement of his 1919 version without break, suggesting that he did not intend for the movement to be divided into separate sections.

The gradual accelerando that begins at the end of the opening Tempo molto moderato section leads seamlessly into the Allegro moderato Scherzo section. This fusion is reflected in the score, with four measures of the 4/4 Allegro moderato corresponding to one measure of the previous section. Abraham has pointed out a similar blending of sections in Sibelius' Symphonies No. 2 and No. 3, where the Scherzo and Finale movements are combined into one.

More recent musicologists have disagreed with this separation, arguing that both sections are based on the same material and can be analyzed as part of a larger sonata form structure. Regardless of how it is interpreted, the first movement of Sibelius' Symphony No. 5 is a masterclass in thematic development and rhythmic complexity, showcasing the composer's unique ability to blend contrasting elements into a cohesive whole.

To download Sibelius' Symphony No. 5, you can search online for 'Sibelius 5 download' or visit your local music store to purchase a recording of the piece.