I think the Heal song would be cool, better than the blast dam. one. Just doesn't seem as powerful for some reason.
Blackmore's idea about the 'reverse wraithform' song seems really cool, if kept so its not unbalancing. It would most likely be a Avatar song, as thats really good, but there are already ways to hit etheral mobs with some things (etheral poison, wraith touch, etc.), so not completely overbalancing, as long as it is limited (like blackmore said, 1 outof 5-10 hits getting through would be about right). I think that would be alot cooler of a song than a +spell dam song.
Any thoughts on the 'skills song', or whether it is even code-able?