This is bar 66 of Chopin’s Étude Op. 10, No. 5. The red F is noteworthy because it’s the only point in the whole composition where the right hand touches a white key — apart from that, it plays black keys exclusively.

Jascha Heifetz once asked Ayke Agus to close her eyes while he played the piece for her. “It sounded strange,” she wrote, “and when I peeked I saw that he was playing it with an orange.”