Have you ever tried to sing while going under a tunnel? DH was driving while listening to Lady Gaga's Bad Romance on the radio. In the middle of the song, we reached a tunnel and decided to "continue" Bad Romance. "Ra ra ah ah ah Roma Roma-ma"... we wanted to see if we got to the same melody when we're on the other side of the tunnel. Youuhooo... we matched the melody... after a few struggles!
The power of repetition... you see it in TV advertisements, constant replays of songs on the radio, etc.