Franz Liszt was a huge fan of Paganini because of his incredible skill, and the technicality of his music. This led him to set out and compose a set of etudes[^1] inspired from Paganini's works. He originally released them in 1838 as the "Études d'exécution transcendante d'après Paganini", then revised them in 1851, dedicating the later revision to Clara Schumann[^2]. He made this revision because the first versions were so absurdly difficult that they were considered impossible to play by many. Even after the revision, many consider these some of the most technically demanding works in piano literature.
Liszt fell very ill, to the extent that an obituary notice was printed in a Paris newspaper, and he underwent a long period of religious doubts and pessimism.