The initial slow section is characterized by the slow tempo, often marked grave or lent, but it is also well known for its dotted rhythms, which are when notes of longer duration alternate with notes of shorter duration. Another typical feature in the slow section is the tirade, which is a flourish of sixteenth notes, notes of very short duration for a slow section, usually moving up the scale.
For texture, the slow section is characterized by homophony. That is, the melody is played by one set of instruments, and the other instruments are merely accompanying the melody in the same rhythm or simply harmonizing the melody. Finally, the slow section closes on the dominant (as opposed to tonic) harmony, so that the ear expects the piece to continue. Musically, the dominant harmony leaves the listener feeling that the work is unfinished or incomplete. In contrast, ending on the tonic sounds like "home" and lends a sense of completion.
The fast section is generally characterized by its contrast with the slow section. Not only is the tempo much faster but also the texture has changed to a contrapuntal, polyphonic style. This fugal texture, in which each set of instruments will stagger their entries playing the same melody, provides a complex sound even while only one melody is being played. A fugal texture sounds similar to a campfire song that is sung in a "round."
Meter is another point of contrast with the slow section. The fast section has a ternary meter, with some multiple of three beats per measure; the slow section has binary meter, with two or four beats per measure. For the harmony, the fast section ends on the tonic. The only time it doesn't end on the tonic is if there is a subsequent coda, or short return to the material from the slow section, which was a stylistic feature of later overtures.