Katja's Waltz comes from Grand Theft Auto IV, the 2008 open-world game from Rockstar Games, where its gentle piano theme became known as a distinctive in-game ringtone. As players shared clips and ringtones from Liberty City online, the melody travelled beyond the game itself and began appearing in fan edits, compilations, and soundboards. It has stayed popular because it is instantly recognisable to GTA players yet soft enough to work as an everyday ringtone, keeping a small piece of the game's atmosphere alive long after release.