Haruki is entranced by Setsuna's singing on the rooftop, and plots to get her to join the Light Music Club no matter what.  But she hates standing out, so convincing her is incredibly difficult.  Meanwhile, the club has an even bigger problem.  The elite student from Music Room 2 he was trying to persuade to join his club as the keyboard player isn't a member of the Music Class, it's a mysterious person whose class and identity are a total unknown.
I used to hear that song once in a while.
Ich höre mir dieses Lied 
von Zeit zu Zeit an.
A veces escuchaba esa canción.
A veces escucho que la tocan.
J’écoutais cette chanson 
de temps en temps.
Às vezes, eu ouço essa música.