Canibri Cowards song from Bog Standard is one of the most inspired uses of song/poetry in fantasy. (Book 4? Spoilers)
Not sure if this was in Book 4 or 3, but...
I think people might not realize how rare it is for a fantasy book to have a meaningful, impactful song/poem, with most songs being an arena for writers to flex their flowery language muscles, and in most cases being a boring experience for readers.
I honestly want to read/hear it every time I remember the song. I also feel like going back and reading that mini-arc because of how impactful it feels, and the title it later inspired.
Provoking a people from a warrior culture into courageous action by suggesting that it is 'okay' to be a coward is an inspired approach that I can tell you, from my experience with such people, would work in many cases, especially one where their homes and families are under attack.