Song of Battle is probably the least useful of the sphere-granting attachments. There isn't a particular reason for wanting a Tactics icon in any given deck. Often it's used to get weapons in a low threat, staging area attack deck, but outside of corner cases like that, it's just a generally useful glue card.
Song of Battle
Attachment. Cost: 1.
Attach to a hero.
Attached hero gains a resource icon.
We go, we go, we go to war, to hew the stone and break the door. The Two Towers
The Dead Marshes #104. Neutral.