linguistic:paraphrasing
I. Allegro maestoso

The first movement is marked Mit durchaus ernstem und feierlichem Ausdruck (With complete gravity and solemnity of expression). It is written in C minor, but passes through a number of different moods and resembles a funeral march.

The movement's formal structure is modified sonata form. The exposition is repeated in a varied form (from rehearsal number 4 through 15, as Ludwig van Beethoven often did in his late string quartets). The development presents several ideas that will be used later in the symphony, including a theme based on the Dies irae plainchant.

Mahler uses a somewhat modified tonal framework for the movement. The secondary theme, first presented in E major (enharmonic of F ♭ major, Neapolitan of E ♭), begins its second statement in C major, a key in which it is not expected until the recapitulation.

The statement in the recapitulation, coincidentally, is in the original E major (F ♭ major). The eventual goal of the symphony, E-flat major, is briefly hinted at after rehearsal 17, with a theme in the trumpets that returns in the finale.

Following this movement, Mahler calls in the score for a gap of five minutes before the second movement. This pause is rarely observed today. Often conductors will meet Mahler half way, pausing for a few minutes while the audience takes a breather and settles down and the orchestra retunes in preparation for the rest of the piece. Julius Buths received this instruction from Mahler personally, prior to a 1903 performance in Düsseldorf; however, he chose instead to place the long pause between the fourth and fifth movements, for which Mahler congratulated him on his insight, sensitivity, and daring to go against his stated wishes.

A practical way of following Mahler's original indication is to have the two soloists and the chorus enter the stage only after the first movement. This creates a natural separation between the first movement and the rest of the symphony and also saves the singers more than twenty minutes of sitting on stage. One can get an idea of Mahler's intention through a comparison with his Symphony No. 3, where – due to the length of the piece – a real break after the first movement (as between two acts of an opera) is highly recommended, and indeed indicated by Mahler. As in the case of Symphony No. 2, this is not always observed nowadays.