Harmonium rhymes with:
ammonium, pandemonium, ammonium, gonium, pandemonium, plutonium, polonium, zirconium, ammonium, capernaum, condominium, cranium, didinium, geranium, gonium, hafnium, millennium, minium, neptunium, pandemonium, plutonium, polonium, selenium, titanium, uranium, zirconium
Harmonium sounds like:
harahan, haran, harem, haren, harima, harm, harman, harmen, harmon, harmonia, harmonie, harmony, harn, harne, harney, harren, harriman, harron, harroun, harryman, haryana, hearin, hearn, hearne, hearon, hearron, heeren, heermann, herein, herin, herm, herman, hermann, hermenio, hermia, hermie, hermina, hermine, herminia, herminie, hermon, hern, hernan, herne, hernia, hernon, heroin, heroine, heron, herren, herriman, herrin, herrman, herrmann, herron, herronimo, heryana, heuerman, heuermann, hiram, hirano, hirayama, hirn, horan, horen, horine, horman, hormann, hormone, horn, horne, horney, horny, hourihan, hren, hron, hurm, hurn, hurney, huron