Personally I like the fact that it's GAIN negative integers. It makes it very consistent with GAINING positive integers.
On another note, (xD) I've liked all your melodies so far. I was actually planning some elemental melodies myself, looking for tunes that could be started once the card was played. In this way there could be a bit more music in-game.
I believe you also mentioned that these melodies do not last forever. You should note how long they do indeed last, I think 3 turns should be enough, and that the effects of the melodies disappear once the melody permanent is gone.
Good ideas all in all Astraic.