For most of the book, I would give Crescendo 3.5 stars, but decided to give it a solid 4 stars by the end.
Crescendo is a good sequel to Counterpoint, but there were some things I didn't really enjoy. For one, I felt that Ayden is constantly the one to sacrifice more in his relationship with Freyrik. Sure, one can argue that Freyrik has no choice in the matter (and there is truth to that), but it got to the point where I wanted to tell Ayden, "Screw it and just LEAVE him!"
There wasn't much action going on until the end of the book. Mostly, just a lot of plotting and waiting around (with Ayden getting beaten several times in each chapter, and Freyrik WISHING he could do something). But things picked up in the end and the book left a good impression overall.