"Glee Club - Rhythm Heaven" is a high quality rip of "Glee Club" from Rhythm Heaven.
When the third choir kid, the one on the far right, sings his note, it's replaced with a Loud Nigra scream. This also happens when the conductor says, "Together now!", the Loud Nigra scream becomes high-pitched. Later, at 0:39, the notes sung by the 3 chorus kids are tuned into "Meet the Flintstones", until 0:52.