I decided to write my own review on Song of the Dead to expand on my response to AndyB's previous review. A couple of weeks ago, I most likely would have agreed completly with that evaluation of the card, but after having played quite some Agnes and Daisy solo decks, I came to really like Song of the Dead.
Sure, the +2 damage is far too unreliable, so let's just forget about that part of the card text and we end up with a rather cheap, very reliable damage spell that deals one damage to an enemy ... that IMO fills a very important slot for solo spellcasting investigators. You won't use this to deal damage to a boss enemy or a Conglomeration of Spheres, that's what Shrivelling is for, but if you have to deal with all enemies yourself you will encounter several weaker enemies that you don't want to waste your precious Shrivelling charges on. That means either packing a weapon ... or Song of the Dead.
The three investigators that can take that card (after core + Dunwich) are Daisy, Agnes and Jim, so let's look if and how they can profit from Song of the Dead in solo play:
Daisy Walker: if you play a caster Daisy with Higher Education, Song of the Dead should almost be an auto-include. You don't have access to good weapons and all alternate damage dealers like Mind over Matter are far too expensive to waste them on Swarm of Rats or Whippoorwills.
Agnes Baker: Propably not as important as for Daisy, because any Agnes deck should have a way to use her ability to deal with weenies, but that also means that you might be able to kill 2 hp enemies with a single Song charge. In addition, with the Fire Axe you have a good weapon alternative, but that might mean some investment in additional resources to fuel the Axe, so Song of the Dead might be the more reliable solution.
Jim Culver: Song of the Dead seems to be tailor-made for Jim , but ironically I think he needs it the least; with a higher -stat and access to the Machete he can handle lesser enemies quite well without it.