In my experience, most string quartets tend to consist of four movements. It seems to be the standard Classical form for this type of ensemble. The first movement is usually marked as Allegro, which means fast in Italian. This movement is typically structured in sonata form.
Sonata form is a musical structure that consists of three main sections – the exposition, development, and recapitulation. In the exposition, the main themes or melodies are introduced. These themes are then explored and developed in the development section, where the music often takes unexpected turns and explores different keys. the recapitulation brings back the themes from the exposition, but this time they are usually in the same key as the beginning.
After the energetic first movement, the quartet often moves on to the second movement, which is usually slower in tempo. This movement provides a contrast to the fast-paced opening movement and allows for more expressive and lyrical music. It can be marked as Adagio, Lento, or Andante, indicating a slower tempo.
The third movement of a string quartet is typically a minuet or a scherzo. This movement is usually in triple meter and provides a lively and rhythmic interlude. The minuet is a more elegant and courtly dance form, while the scherzo is often more playful and energetic. Both forms offer a lighter contrast to the intensity of the first and second movements.
The string quartet concludes with the fourth movement. This movement is often marked as Presto or Allegro, indicating a fast tempo. It brings the quartet to an exciting and energetic conclusion, often showcasing virtuosic passages and a sense of resolution.
Of course, there can be variations in the number and order of movements in a string quartet, depending on the composer and the specific composition. Some quartets may have more than four movements, while others may combine different forms or omit certain movements altogether. However, in my experience, the four-movement structure described above is the most common and widely recognized in the repertoire of string quartets.