I have a friend who, whenever two words are uttered, will complete it to reveal a song title. For example, if I begin "If only..", before I can get any further, he's added "...have eyes for you". With me, it's a couple or more of notes which will trigger a tune. For example, there are trains in North Wales (and elsewhere for all I know) that emit two notes,with a certain slow and majestic tempo, that takes me immediately to the beginning of The Great Gate of Kiev from Mussorgsky's Pictures at an Exhibition. Other trains emit notes that to my ear have the same interval but at a higher pitch and much faster tempo, making the start of Colonel Bogie. Probably my favourite, though, is the jingle on the Tannoy at Geneva Airport, which consists of 4 or 5 notes which happen to be the start of How Much is that Doggy in the Window?
Now in these days of all manner of electronic devices emitting random notes, often for no obvious reason, there must be other examples of this.