The Signet Ring: A Trouvères Adventure by Ellis L Knox

Never trust a noble, even if one hires you. The Trouvères are invited to an island to perform at a celebration: a peace treaty between two long-time enemies and a betrothal to seal the deal. Val, the head of the troupe of humans, plus an elf and an ogre, has a plan: give a good show, get good pay, and get out.