The Midnight Orchestra by Jessica Khoury is the sequel to The Mystwick School of Musicraft. I do recommend reading in order.
Amelia must master the magic of Composing to help her school win a magic competition—and save her friends from a mysterious evil. Things are finally looking up for Amelia Jones: she's officially a Mystwick student, and she even has a teacher to help her learn how to use her rare Composing magic. When Mystwick enters an international magic competition, it’s Amelia's chance to Compose something that will help them win the day. The only problem is that she still doesn’t understand how her powers work. But then she hears about a super exclusive Midnight Orchestra—half performance, half magical black market—and Amelia is sure that’s where she’ll find the answer to her Composing problem. But the Midnight Orchestra is far more sinister than it initially appears and if Amelia can’t unlock her Composing powers, not only will Mystwick lose the musicraft competition, she won’t be able to rescue her friends from the danger unleashed in this thrilling adventure.
The Midnight Orchestra starts off right after the first book ended, and I will admit that it took me a bit to remember just where everyone and everything left off. However, once I got back into the swing of things I was again empathizing with Amelia and all her insecurities and feelings as she tried to work through so many things at once. Her struggles with friendship are something that many readers can relate to, and the complicated feelings about family and the trustworthiness and intelligence of the adults around here is equally understandable. I was engaged in her struggles quickly, and while some of the big reveals I had figured out much earlier, I think that is more because of the number of magic and mystery books that I have read rather than any flaw in the writing. I think that Amelia continues to grow as a character and that fans of the first book will definitely want to pick this one up as well.
The Midnight Orchestra is a charming continuation of the series, and will please fans of the series. As a side note- if you enjoy audiobooks, a version of this title (with music) is already available via Audible. 
