Why did Haydn keep the melody unchanged in the second movement of his string quartet in C Major, op. 76, no. 3?

The melody remains unchanged in the second movement of Haydn's string quartet in C Major, op. 76, no. 3 because it is associated with Emperor Franz II, symbolizing steadfastness. This linkage to the emperor is significant, as the work itself pays homage to the nobility and highlights themes of loyalty and stability. By retaining the melody, Haydn reinforces its importance and significance, allowing the audience to appreciate not only the beauty of the music but also its deeper connections to historical figures and ideals. This approach emphasizes the value of the melody as a tribute, rather than focusing on intricate variations or improvisation, which would detract from its intended message.