Make sure that the music volume in the FacilityMeltdown config is set to 0, otherwise you will hear both the Custom music and the default music from the Meltdown mod simultaneously.
If you find the music to be too loud or quiet, I recommend changing the master volume in the PizzaTowerEscapeMusic config to a value that you prefer.
Atsuhiro Motoyama - Parapsychology (Battle Bakraid)