Please read Alexey Sklyarenko's annotations on Pale Fire, Ada and other Nabokov works here.
Humbert's chess partner at Beardsley, Gaston Godin (a character in VN's novel Lolita, 1955) is a namesake of Gaston Leroux (1868-1927), a French writer of detective novels, the author of Le Fantôme de l'Opéra ("The Phantom of the Opera," 1909). Among the people with whose photographs Gaston Godin had decorated the sloping wall of his studio is Tchaikovski, a Russian composer (1840-93):