Acapella

The band visits one of their fan's bday party by surprise. May be was cripple. When they were asked to sing a song,  they does an acapella. This is the place where one of the band member meet his future wife. This song contrasts or have same line of the first songs. When one person hears it,  he should know that its similar to first song, that theres a connection. 
This song can also be Paul's brother's song which his sister sang when he was small in the incubator or mother's womb.