Before I managed to get my hands on Ghoulish Song by William Alexander, I first read his earlier book Goblin Secrets (which in retrospect, I liked a bit better, though both are good). They are both set in the same place and time, and little bits of each plot intertwine in a delightful way that makes it worth reading them consecutively. However, only Ghoulish Song is a Girls Underground book.
Kaile lives with her mother and father (who are mostly distracted by running their bakery) and annoying little brother in the city of Zombay. One day she lets a troupe of performing goblins put on a play in the shop, and one of them gives her a bone flute in thanks. However, playing the flute somehow makes Kaile’s shadow separate from her – and according to the traditions of Zombay, this means she is dead, a ghoul, and she is summarily exiled from her home and society. Her shadow, who she names Shade, stays near her from habit but is a reluctant companion at best. Kaile sets off in search of answers and the means to re-attach her shadow and resume her normal life. She discovers that the flute is somehow tied to a drowned girl, and the coming floods that may destroy the city. Helped by musicians, threatened by the keeper of the town reliquary, and alone but for her grumpy shadow, Kaile ends up facing a terrifying ghoul made of drowned people and saving the day with the magical musical ability she inherited from her grandfather. In the end, she is re-united with her shadow and welcomed back to the world of the living.