How did Haydn share thematic material among the instruments in the Russian Quartets?

In his Russian Quartets (Opus 33, 1781), Joseph Haydn introduced what he described as an "entirely new manner" of composition.1

Departing from earlier practices where the first violin typically dominated as the principal melody instrument, Haydn ensured that thematic material was more equally shared among all four stringed instruments. This approach moved away from the texture where lower voices served merely as accompaniment, allowing the cello and viola to participate actively in the thematic work. By distributing these musical ideas across the ensemble, Haydn established a more balanced and integrated string quartet texture that became a hallmark of his later style.12