The mysterious, ghost-like voice that can be faintly heard on the soundtrack during the playing of Pablo de Sarasate's 1904 recording of his own 1878 composition, Zigeunerweisen (which gives this film its title), and which the film's characters comment upon at great length, is not a fabrication of the filmmakers. On the original recording, at about 3 minutes and 25 seconds, a voice can be heard speaking rapidly for about two seconds. The two main characters in the film have no idea what the voice is saying and it intrigues them. However, according to a biography of the violinist-composer Efrem Zimbalist Sr. (father of the famous film and television actor), Sarasate was actually "instructing his accompanist to cut the slow section" of the composition, presumably to accommodate the limited recording time of the disk.
Zigeunerweisen means something like gypsy tunes or melodies in German.