Pandemonium rhymes with:
ammonium, harmonium, ammonium, gonium, harmonium, plutonium, polonium, zirconium, ammonium, capernaum, condominium, cranium, didinium, geranium, gonium, hafnium, harmonium, millennium, minium, neptunium, plutonium, polonium, selenium, titanium, uranium, zirconium
Pandemonium sounds like:
pantano, pantheon, pantomime, panton, pentane, pentium, penton, phantom, pondimin, ponton, pontoon, poynton