Pokemon like Meloetta are said to have a wonderful voice and her songs are supposed to be soothing. As such, the song of Jigglypuff can put you to sleep. Put together the singing pokemon, and you'd probably get a pokemon choir.
But however much the songs are good - does Perish Song sound good? I had only seen it once in the anime (Pokemon Crystal), and it seemed to hurt the opponent pokemon.
Is it some sad mourning song that makes you faint? Or an ear-splitting screech that literally kills your ears?